High Resistance Ground Unit For Use on 480 and 600 Volt Wye and Delta-Connected Sources 50 or 60 Hertz Systems

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1 High Resistance Ground Unit For Use on 480 and 600 Volt Wye and Delta-Connected Sources 50 or 60 Hertz Systems Sistema de resistencias de puesta a tierra Para su uso en sistemas de 50 ó 60 Hz con fuentes conectadas en estrella o delta de 480 y 600 V Système de résistances de mise à la terre élevées Pour une utilisation sur des sources de 480 et 600 V raccordées en étoile et triangle Systèmes de 50 ou 60 Hertz Class / Clase / Classe 6036 Instruction Bulletin Boletín de instrucciones Directives d'utilisation Retain for Future Use. / Conservar para uso futuro. / À conserver pour usage ultérieur.

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3 High Resistance Ground Unit For Use on 480 and 600 Volt Wye and Delta-Connected Sources 50 or 60 Hertz Systems Class 6036 Instruction Bulletin Retain for future use.

4 ENGLISH HAZARD CATEGORIES AND SPECIAL SYMBOLS Read these instructions carefully and look at the equipment to become familiar with the device before trying to install, operate, service or maintain it. The following special messages may appear throughout this bulletin or on the equipment to warn of potential hazards or to call attention to information that clarifies or simplifies a procedure. The addition of either symbol to a Danger or Warning safety label indicates that an electrical hazard exists which will result in personal injury if the instructions are not followed. This is the safety alert symbol. It is used to alert you to potential personal injury hazards. Obey all safety messages that follow this symbol to avoid possible injury or death. DANGER DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury. WARNING WARNING indicates a potentially hazardous situation which, if not avoided, can result in death or serious injury. CAUTION CAUTION indicates a potentially hazardous situation which, if not avoided, can result in minor or moderate injury. CAUTION CAUTION, used without the safety alert symbol, indicates a potentially hazardous situation which, if not avoided, can result in property damage. Provides additional information to clarify or simplify a procedure. PLEASE NOTE Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. No responsibility is assumed by Schneider Electric for any consequences arising out of the use of this material.

5 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Table of Contents TABLE OF CONTENTS Section 1 Introduction... 5 Section 2 Safety Precautions... 7 Section 3 Receiving, Handling, Storage, and Installation... 8 Receiving... 8 Handling... 8 Storage... 8 Installation... 8 Section 4 Typical High Resistance Grounding System... 8 Low Voltage Systems... 8 Control Power Transformer (CPT)... 8 Derived Neutral... 8 Resistor and Enclosure Material... 9 Resistor Unit... 9 Equipment Enclosure... 9 Principles of Operation Ungrounded Systems High Resistance Grounding Pulse Fault Locator Circuit Ground Detection and Alarm Ground Current Detector System Capacitive Charging Current Selection of Ground Resistor Value and Connections Resistor Circuit Diagrams Door Components Alarm Horn Ammeter Red Light Green Light Amber Light Silence Button Reset/Manual/Auto Switch Normal/Pulse Switch Test Button Voltmeter Relay Internal Components Start-Up Procedures HRG System Diagrams Ground Detection System Test Use of the System Under Actual Grounded Condition Power System Revisions Records System Initial Installation Voltmeter Readings Voltmeter Relay Set Points System Faults Section 5 Inspection and Maintenance Section 6 Nameplate Information Section 7 Accessory Equipment Portable Ground Current Detector Section 8 Installation and Maintenance Logs ENGLISH Schneider Electric All Rights Reserved 3

6 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources List of Figures and Tables 06/2008 ENGLISH LIST OF FIGURES Figure 1: Diagrams of Wye and Delta Systems... 6 Figure 2: Derived Neutral Configuration... 9 Figure 3: Typical Resistor Assembly... 9 Figure 4: Ground Current Detector Figure 5: Resistor Circuit Diagrams Figure 6: Door Component Locations Figure 7: Internal Components Figure 8: Typical High Resistance Ground System Used on Wye Systems Figure 9: Typical High Resistance Ground System Used on Delta Systems Figure 10: Ground Detector with Case LIST OF TABLES Table 1: Resistor Connection Charts Table 2: System Initial Installation Table 3: Voltmeter Readings Table 4: Voltmeter Relay Set Points Table 5: System Faults Table 6: Maintenance Log Schneider Electric All Rights Reserved

7 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 1 Introduction Section 1 Introduction This bulletin contains instructions for the theory, operation, and maintenance of high resistance ground systems manufactured by Schneider Electric. High resistance grounding equipment provides a high resistance grounding circuit for ungrounded power systems. Depending upon the options selected, high resistance grounding equipment offers the following functions: Provides system stability and prevents overvoltages by damping high frequency system oscillations due to ground faults and other system disturbances. Provides a way to detect and warn of the first ground fault that occurs within the system. Provides a means of monitoring the condition of the system voltage in relation to ground potential by means of voltage measurements. In the event of a line-to-ground fault event, provides a way to pulse the ground fault current so the path of ground fault current can be traced by a portable detector. Enables the system to continue to operate with a single line-to-ground fault present. These functions are accomplished with system neutral grounding adjusted so that ground fault currents are only slightly higher than the natural capacitive charging currents of the ungrounded systems. By selecting the appropriate options, high resistance grounding equipment is suitable for Wye or Delta ungrounded configured systems rated for 480 and 600 volts nominal. See Figure 1 on page 6. Control circuits typically operate on 120 Vac. ENGLISH This guide covers several applications of grounding equipment. The illustrations and procedures are general in nature. Your equipment may be different from the illustration shown on page 6. Refer to the factory shop drawings supplied with the low voltage equipment. The descriptions and specifications contained in this guide were in effect at the time the guide was approved for printing. Schneider Electric reserves the right to discontinue models at any time, and to change specifications or design, without notice or incurring obligation. The equipment described within this guide may or may not be identified as either standard or optional. If results described within this manual are not produced when testing, inspecting, or installing this equipment, and the immediate cause cannot be determined, contact Square D Field Services at Schneider Electric All Rights Reserved 5

8 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 1 Introduction 06/2008 Figure 1: Diagrams of Wye and Delta Systems ENGLISH From transformer secondary Neutral A B Fuse Fuse Control power transformer (CPT) Fuse Pulse contactor Resistor Voltage meter relay Panel lights Normal G R Selector switch (Normal / Pulse) Ground Fault Circuit Diagram Showing Wye Systems From transformer secondary A B C Fuse Fuse Grounding transformers Control power transformer (CPT) Fuse Pulse contactor Resistor Voltage meter relay Panel lights Normal G R Selector switch (Normal / Pulse) Ground Fault Circuit Diagram Showing Delta Systems Schneider Electric All Rights Reserved

9 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 2 Safety Precautions Section 2 Safety Precautions DANGER HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E. This equipment must be installed and serviced only by qualified personnel. Perform such work only after reading and understanding all of the instructions contained in this bulletin. Turn off all power supplying this equipment before working on or inside equipment. Assume that all circuits are live until they have been completely de-energized, tested, locked out, and/or tagged out (per OSHA ). Pay particular attention to the design of the power system. Consider all sources of power, including the possibility of backfeeding. Always use a properly rated voltage sensing device to confirm power is off. Carefully inspect your work area and remove any tools and objects left inside the equipment. Replace all devices, doors, and covers before turning on power to this equipment. ENGLISH Failure to follow these instructions will result in death or serious injury CAUTION HAZARD OF EQUIPMENT DAMAGE OR INJURY Proper selection of ground resistance value is required for proper operation of the high resistance grounding system. As electrical system parameters change over time, the grounding resistance may need adjustment. Verify proper selection of the grounding resistance when electrical system changes are made, and on an annual basis. Failure to follow these instructions can result in injury or equipment damage. DANGER HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Connect system neutral to ground only through the grounding resistance. Failure to follow this instruction will result in death or serious injury Schneider Electric All Rights Reserved 7

10 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 3 Receiving, Handling, Storage, and Installation 06/2008 ENGLISH Section 3 Receiving, Handling, Storage, and Installation Receiving Before leaving the factory, high resistance grounding equipment is given a final inspection, both mechanical and electrical. Upon receipt, immediately inspect the equipment for damage. If the equipment is damaged, immediately file a claim with the carrier. Include all pertinent information with the claim, such as description of damage, shipping crate numbers, and requisition numbers. Handling Storage Installation Section 4 Typical High Resistance Grounding System Low Voltage Systems Control Power Transformer (CPT) Derived Neutral High resistance grounding equipment is shipped in an upright position, either as part of a low voltage equipment or as a single stand-alone section. Maintain the equipment in an upright position. Refer to the specific low voltage equipment installation bulletin for handling information. Store the high resistance ground equipment per the instructions provided in the low voltage equipment installation bulletin. Install the high resistance ground equipment per the instructions provided in the low voltage equipment installation bulletin and as shown in applicable drawings provided with the equipment. High resistance ground (HRG) systems are designed for application on 480 and 600 volt ungrounded Delta and ungrounded Wye, 50 and 60 hertz power systems. Systems are specific for each type, voltage, and frequency and are specified on order entry. Refer to the factory shop drawings for specified ratings. A separate dry type control power transformer (CPT) may be provided as necessary to supply control voltage for the HRG controls. These transformers are provided with the appropriate primary and secondary fuses. Control power also may be obtained from the low voltage equipment in which the HRG is installed. If the power system incorporates a Delta-connected transformer or an ungrounded Wye transformer where the neutral terminal is not available, a derived neutral must be created. High resistance grounding systems by Schneider Electric use the Wye-Delta type derived neutral, as shown in Figure 2 on page 9. Three single-phase transformers are connected in a Wye-Delta configuration. The ratings of these transformers are based in part on system voltage and maximum current drawn through the grounding resistor during a ground fault. These transformers are specific to the power system ratings and are shown on the factory shop drawings. The primary windings of these transformers are connected in Wye with each winding connected to a phase conductor of the system. The common connection of each primary winding provides a derived neutral to which the grounding resistor is connected. The secondary windings of these transformers are connected in a Delta configuration. An equivalent current will circulate in the secondary windings as a reflection of current flowing in the grounding resistor. See Figure 9 on page 19 for a line diagram of a typical high resistance ground system used on Delta systems Schneider Electric All Rights Reserved

11 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Figure 2: Derived Neutral Configuration Primary A B C ENGLISH Secondary R Wye-Delta Type Derived Neutral Resistor and Enclosure Material Resistor Unit The resistor unit consists of a group of industrial resistors arranged to provide the proper resistance and capacity to dissipate heat under all operating conditions. The resistor unit may be mounted in an internal compartment in the low voltage equipment. When mounted in the low voltage equipment, the compartment is adequately ventilated to dissipate the heat developed during ground fault conditions. If the desired compartment cannot be sufficiently ventilated, or if one is not available, the equipment resistor unit is mounted on top of the equipment or in some remote location. Figure 3 illustrates a typical resistor assembly. Figure 3: Typical Resistor Assembly Equipment Enclosure The high resistance grounding equipment is typically mounted within the low voltage equipment. The high resistance grounding system also may be mounted in a separate NEMA Type 1 or NEMA Type 3R freestanding unit. When the enclosure is supplied as a freestanding unit, the grounding resistor is typically mounted and ventilated within the enclosure Schneider Electric All Rights Reserved 9

12 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 Principles of Operation ENGLISH Ungrounded Systems In many situations, the National Electrical Code (NEC) requires electrical systems to be grounded by some means. Solidly grounded systems have the advantage of ensuring that the potential on any conductor is no higher than the maximum system single-phase voltage. However, in some industrial applications, ungrounded systems have an advantage in system reliability because the first ground fault will not disrupt electrical service as it would for solidly grounded systems. This has particular importance for continuous industrial processes. In an ungrounded system, if one conductor becomes grounded due to insulation failure at any point in the system, then that conductor assumes ground potential, and the remaining two conductors assume a line-to-line potential with respect to ground. If no other ground faults exist involving the other two conductors, an ungrounded system may continue to operate. If the single line-to-ground fault is not solid, and has an arcing characteristic, an ungrounded system may experience unusually high line-to-ground voltages at relatively high frequencies. This high voltage is a result of the conductor inductance, conductor-to-ground capacitance, and the intermittent characteristics of the arcing fault. In this case, the system neutral and three-phase conductor voltages are displaced significantly from ground potential. This is undesirable because system insulation is overstressed. The HRG system minimizes these high voltages and frequencies by dampening or reducing the effects of capacitance and inductance inherent in the power system. High Resistance Grounding Pulse Fault Locator Circuit Ground Detection and Alarm The fundamental purpose of high resistance grounding is to provide sufficient system damping to overcome the negative effects of arcing ground faults and at the same time retain all of the advantages of an effectively ungrounded system. A resistance value is selected sufficient to limit the overvoltage during arcing faults, but not low enough to draw excessive ground fault current. The resistance value should be selected relative to the system capacitive charging current. The system capacitive charging current is proportional to the capacity of the system and the types of components used within the electrical system. Since the fault current with high resistance grounding can be similar in magnitude to the charging currents, it is difficult to distinguish between the two. A pulsing circuit is provided to momentarily increase the fault current by intermittently short-circuiting part of the grounding resistance. The pulsing current can be detected within the grounded circuit due to a more noticeable flicker of the ground current detector ammeter. The pulse locator circuit is initiated only when a fault has been detected and the Normal/Pulse switch is set to the Pulse position. Ground detection is accomplished through a contact-making voltmeter relay, or similar device, that monitors the voltage across the grounding resistance. Under ideal conditions, the voltage is zero if the system capacitance within all three phases is balanced. If it is unbalanced, which is normal, the meter shows a small voltage, proportional to the degree of capacitance unbalance, across the grounding resistance. The voltmeter relay is provided with two user-adjustable set points and an adjustable time delay. The lower set point is wired to terminal blocks for customer use. A typical application may be to set the lower set point just above the nominal charging current, approximately 5 10%. This setting is based on the history of the system operation or on analysis of the charging current measured. In this manner, a slight increase in charging current can be detected and signaled to a remote panel without activating the high resistance ground alarm circuit. Alternatively, it can be used to trigger an alarm if the resistor is disconnected or open-circuited Schneider Electric All Rights Reserved

13 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Ground Current Detector The upper set point is used to trigger the alarm circuit. This set point should be set approximately 10 20% above the nominal charging current. The alarm will be activated when the charging current exceeds this value for the specified time delay setting. See Section 8 Installation and Maintenance Logs on pages for charts on which to log this data. The detector measures the leakage current caused by a ground fault. It enables the operator to locate failures quickly. See Ground Detection System Test and Use of the System Under Actual Grounded Condition on page 20 for instructions. The detector is a clamp-on current transformer and ammeter that is sensitive to ac currents passing through it. The detector is moved within the power system following the path of pulsating ground current. If the meter needle flickers, the detector is in a circuit that contains a ground fault downstream. If it does not flicker, the ground fault is in a different circuit or the detector is downstream from the fault location. The detector must encompass all current-carrying conductors in the circuit. It makes no difference whether the circuit is three-phase or single-phase. The detector measures the leakage current to ground. Figure 4 illustrates a method of using the ground current detector. ENGLISH Figure 4: Ground Current Detector Source A C B Leak R System Capacitive Charging Current The maximum system capacitive charging current must be known in order to optimize the setting of the ground resistor taps. The system charging current should be measured with all components of the power system connected to ensure the total capacitive current is measured. Note these values below. NOTE: Because of the inherent danger involved in measuring the system capacitive charging current, Schneider Electric recommends consulting with a suitable testing firm for assistance in obtaining these measurements. Measured Charging Current: I a = ; I b = ; I c = The charging current of the system is the average of these three measurements shown by the following formula: (I a + I b + I c ) I C = Schneider Electric All Rights Reserved 11

14 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 ENGLISH Selection of Ground Resistor Value and Connections After determining the value of the system capacitive charging current (I C ), calculate the resistance value (R) according to the following formula: R = Line-to-Line Voltage / (1.732 x I C ) The resistance values available with standard resistor connections are likely to be different than calculated. Since the selection is not critical, a value is selected which is just lower than the calculated value. This ensures a maximum ground current slightly higher than the system charging current and allows for adequate system damping to minimize ringing. Table 1 lists various resistance values that are available in a typical resistor bank. Refer to the factory order drawings for specific settings available.the equipment is shipped from the factory with the resistors connected for the lowest current value. Table 1: Resistor Connection Chart Connection Diagram (Figure 5) Normal Connected Resistance (Ohms) 5A Pulse-Connected Resistance (Ohms) 5B C D 55.4 Resistance calculations are based on standard Schneider Electric resistor connections for a 480 V power system. Resistor Circuit Diagrams See Figure 5 on page 13 for typical resistor configurations and the following paragraphs for descriptions of each configuration. 5A Under ground fault conditions, the total resistance is ohms. This produces 1 A of ground fault current. During the pulse ON cycle, the contactor contact C closes, shorting part of the resistor. This decreases the total resistance to 39.6 ohms, thus increasing the current (pulse current) to 7 A. 5B Under ground fault conditions, the total resistance is ohms. This produces 2 A of ground fault current. During the pulse ON cycle, the contactor contact C closes, shorting part of the resistor. This decreases the total resistance to 39.6 ohms, thus increasing the current (pulse current) to 7 A. 5C Under ground fault conditions, the total resistance is 92.3 ohms. This produces 3 A of ground fault current. During the pulse ON cycle, the contactor contact C closes, shorting part of the resistor. This decreases the total resistance to 39.6 ohms, thus increasing the current (pulse current) to 7 A. 5D Under ground fault conditions, the total resistance is 55.4 ohms. This produces 5 A of ground fault current. During the pulse ON cycle, the contactor contact C closes, shorting part of the resistor. This decreases the total resistance to 39.6 ohms, thus increasing the current (pulse current) to 7 A Schneider Electric All Rights Reserved

15 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Figure 5: Resistor Circuit Diagrams 5A Meter relay input ENGLISH Fuse R5 Neutral ground resistor R4 R3 R2 R Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω C R6 R5 R4 R3 R2 R1 Connection Shown for 1 A Ground Fault with 7 A Pulse 5B Meter relay input Fuse R5 Neutral ground resistor R4 R3 R2 R Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω C R6 R5 R4 R3 R2 R1 Connection Shown for 2 A Ground Fault with 7 A Pulse 5C Meter relay input Fuse R5 Neutral ground resistor R4 R3 R2 R Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω C R6 R5 R4 R3 R2 R1 Connection Shown for 3 A Ground Fault with 7 A Pulse 5D Meter relay input Fuse R5 Neutral ground resistor R4 R3 R2 R Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω C R6 R5 R4 R3 R2 R1 Connection Shown for 5 A Ground Fault with 7 A Pulse Schneider Electric All Rights Reserved 13

16 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 ENGLISH Door Components Figure 6 illustrates the door-mounted components of a typical high resistance ground unit. These components are discussed on page 15. Contact your local Schneider Electric representative for replacement parts. Figure 6: Door Component Locations Alarm horn 2. Ammeter 3. Red light: Ground Fault 4. Green light: Normal 5. Amber light: Pulse On 6. Silence button 7. Reset/Manual/Auto switch 8. Normal/Pulse switch 9. Test button 10. Operation nameplate 11. Rating nameplate 12. Voltmeter Schneider Electric All Rights Reserved

17 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Alarm Horn Ammeter Red Light The alarm horn sounds after a ground fault current above the meter relay setpoint is detected. The ammeter displays charging current and actual ground fault current when a ground fault occurs. The red light indicates a system ground fault where the voltage drop across the grounding resistor has increased to a level above the voltmeter set point. The red light remains illuminated until the ground fault is cleared or the system is reset. ENGLISH Green Light Amber Light Silence Button Reset/Manual/Auto Switch Normal/Pulse Switch Test Button Voltmeter The green light indicates that control power is available and the system is operating normally. The green light is turned off when the voltage drop across the ground resistor has increased to a level above the voltmeter set point. The amber light indicates when the pulse circuit is on and will flash in sync with the pulse current. This button silences the horn that sounds after a ground fault current above the meter relay setpoint is detected. NOTE: The red fault light will remain illuminated until the ground fault is cleared or the system is reset. This switch selects the alarm reset mode. Manual mode: A ground fault current above the meter relay setpoint will sound the horn and illuminate the red fault light. These indicators will then remain in a latched state, even after the ground fault current falls below the meter relay setpoint. Manually moving the switch to the Reset position resets the system. Auto mode: A ground fault current above the meter relay setpoint will sound the horn and illuminate the red fault light. The system is automatically reset when the ground fault current drops below the meter relay setpoint. This switch turns on the pulse circuit. The pulse circuit is activated by the operator during fault location activity. It may be activated any time a ground fault occurs and when the alarm circuit is energized. When this button is pushed, the voltmeter reading will increase and the alarm relay is picked up. The green light goes out and the red light illuminates. If the Reset/Manual/Auto switch is in the Manual position, moving it to the Reset position restores the system to normal operating conditions. The voltmeter monitors the voltage drop across the grounding resistor. The voltmeter relay is equipped with two contact set points: The lower set point is used as a pre-alarm or first level alarm. Schneider Electric recommends setting the value to a voltage approximately 5 10% higher than the voltage reading associated with the nominal charging current. This contact is wired to terminal blocks for customer use and does not indicate an alarm via the alarm controls. The upper set point is used to activate the alarm circuit upon sensing an increasing voltage drop across the grounding resistor. Schneider Electric recommends setting the value to a voltage approximately 10 20% higher than the maximum voltage drop caused by the maximum charging current under normal conditions Schneider Electric All Rights Reserved 15

18 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 ENGLISH Internal Components Figure 7 illustrates internal components of a typical high resistance ground unit. Contact your local Schneider Electric representative for replacement parts. Figure 7: 1 Internal Components ON OFF Potential transformer 2. Shorting terminal blocks 3. Test circuit disconnect 4. Control power fuses 5. Timing relays 6. Control relays 7. Grounding transformer disconnect (for use on derived neutral systems) 8. Ammeter current transformer 9. Terminal blocks 10. Grounding transformers (for use on derived neutral systems) Schneider Electric All Rights Reserved

19 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Start-Up Procedures DANGER HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Connect system neutral to ground only through the grounding resistance. Failure to follow this instruction will result in death or serious injury. ENGLISH Before start-up, carefully read the danger precaution above. Power systems with a high resistance ground unit shall be grounded solely through the grounding resistance furnished in the high resistance ground unit. Ensure the system is grounded properly before proceeding. 1. Turn off all power supplying this equipment before working on or inside equipment. Always use a properly rated voltage sensing device to confirm power is off. 2. Verify power system is free of ground faults. (Refer to low voltage equipment instruction bulletin.) 3. Verify all phase, neutral, and ground connections have been made between the power system and the HRG system per the factory shop drawings. 4. Based on the system capacitive charging current, reconnect the grounding resistor as necessary. Refer to Figure 5 on page Set the Normal/Pulse control to Normal. 6. Carefully inspect your work area and remove any tools and objects left inside the equipment. 7. Replace all devices, doors, and covers before turning on power to this equipment. 8. With all loads connected and the system energized, set the voltmeter relay lower set point to a position 10% above the actual voltmeter reading. Set the upper set point approximately 20% above the actual reading Schneider Electric All Rights Reserved 17

20 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 ENGLISH HRG System Diagrams Figure 8: Typical High Resistance Ground System Used on Wye Systems 480 Vac line bus A B C N Figures 8 and 9 are diagrams of typical high resistance ground systems used on Wye and Delta systems, respectively. To load breakers Fuse MR Test Neutral ground resistor Ω Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω 120 Vac control power Control transformer Ammeter R Fuse Fuse R1 Provision for jumper connection based on system capactitive charging current calucation. Normal / Pulse R2 Test push button R3 Manual Reset Auto R6 R5 R3 MR R1 MR R6 Horn Normal G MR R1 Ground fault R Manual R3 Auto R2 R4 Pulse ON A R5 Silence push button Schneider Electric All Rights Reserved

21 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System Figure 9: Typical High Resistance Ground System Used on Delta Systems 480 Vac line bus A B C To load breakers Fuse MR ENGLISH Three control power transformers 1.5 kva, 480/120 V Test Neutral ground resistor Ω Ω 46.7 Ω 36.9 Ω 15.8 Ω 39.6 Ω Ammeter 120 Vac control power Control transformer R Fuse Fuse R1 Provision for jumper connection based on system capactitive charging current calucation. Normal / Pulse R2 Test push button R3 Manual Reset Auto R6 R5 R3 MR R1 MR R6 Horn Normal G MR R1 Ground fault R Manual R3 Auto R2 R4 Pulse ON A R5 Silence push button Ground Detection System Test 1. Move the Reset/Manual/Auto switch to the Manual position. 2. Press and hold the Test button for five seconds. The voltmeter reading will increase. The green light goes out, the horn sounds, and the red light illuminates. Any user-supplied warning devices connected to the alarm circuits will operate. 3. Release the Test button. The red light remains illuminated until the operator moves the Reset/Manual/Auto switch to the Reset position. 4. Turn the Normal/Pulse switch to the Pulse position. The amber light begins to flash and the pulse contactor begins to operate in a rhythmic fashion. If the system is normal and some line-to-ground capacitance imbalance exists, a slight pulse in the voltmeter reading occurs. 5. Move the Reset/Manual/Auto switch to the Reset position momentarily, and then back to the Manual position. The red light goes out and the green light again illuminates Schneider Electric All Rights Reserved 19

22 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 4 Typical Resistance Ground System 06/2008 ENGLISH Use of the System Under Actual Grounded Condition Power system ground faults exist in varying forms and degrees of severity. They could be in the form of wet insulation which displaces the neutral a small amount, or could be so severe that one of the phases is solidly grounded. A condition in which all three phases have equal grounding is not detected by this system. This condition is only detected when operating an overcurrent device. Typically, however, only one or two of the phases are affected. In this case, detection is possible. As one or two lines develop a lower resistance to ground, the system neutral is displaced and a higher voltage develops across the grounding resistor. As the resistance of the grounding decreases, the voltage increases and the voltmeter relay indicates a higher reading, as expected for a deteriorating insulation system. When a ground fault occurs, the resistor limits the ground current. The resulting voltage appears across the grounding resistor and is sensed by the voltmeter relay. After a preset, adjustable time delay, a control relay contact opens, which extinguishes the green light ( Normal ) and a control relay contact closes, which illuminates the red light ( Ground Fault ). To locate the fault, turn the Normal/Pulse switch to Pulse. This initiates the pulse relay, alternately energizing and de-energizing a shorting contact across part of the grounding resistor. A rhythmic fluctuation in the magnitude of the ground current results at a fixed rate of 30 pulses per minute. DANGER HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E. This equipment must be installed and serviced only by qualified personnel. Perform such work only after reading and understanding all of the instructions contained in this bulletin. Failure to follow these instructions will result in death or serious injury. The current transformer and ammeter on the panel allow the operator to observe the current fluctuation on the system. Using a portable ammeter (ground current detector), trace the fluctuation of the ground current through the system. Start at a point as close to the supply as possible. Due to large cable sizes and multiple cables per phase, it may not be practical to start at the main distribution panel. Select a branch circuit where the portable detector will encompass all of the three-phase conductors. Any branch circuit in which the detector indicator pulses is the faulted circuit. Repeat this procedure at any downstream panels until the faulted circuit and location can be determined. Usually only one feeder circuit indicates a detectable flicker in the charging current reading. Other feeder circuits may display a continuous charging current which does not indicate a ground fault. Readings taken with the portable ammeter around metal conduit are likely to be ineffective since the ground current may be returning through the grounded conductors. This feeder circuit is then followed to the next distribution point in the system or pull box where it is possible to again encompass all three phases of the insulated conductors Schneider Electric All Rights Reserved

23 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 4 Typical Resistance Ground System If this feeder circuit is further distributed, test each circuit of that distribution individually to see which carries the pulsating current. If, within a single circuit, the pulsating current disappears at a point downstream, the fault is somewhere between the previous point tested and the point where the pulsing current disappears. When the fault is located, the pulse switch may be returned to the Normal position. The red light remains illuminated until the system is repaired and the Reset/Manual/Auto switch is moved to the Reset position. Once the system is restored, check the voltmeter reading. The reading should have returned to a level below the set point and indicate a level approximately equal to the level prior to the fault. If multiple faults exist, the voltmeter reading remains above that which is considered normal. If necessary, repeat this procedure to find other abnormal conditions. ENGLISH Power System Revisions Records A power system may be modified to meet changing needs. If there is a question whether the power system needs to be reset, evaluate the grounding system and reset as if it were a new system. In order to accurately determine the status of a power system, accurate records must be maintained. Keep these records at the end of this manual in the appropriate tables in Section 8 Installation and Maintenance Logs on pages For high resistance grounding systems, record the following: System Initial Installation The original line-to-ground charging currents for each phase The grounding resistor value selected The voltmeter reading as the system was originally established Voltmeter Readings Voltmeter Relay Set Points System Faults Record voltmeter readings at regular intervals. Frequency of reading is dictated by the severity of stress placed upon the system and history of occurrences. Take monthly readings initially; modify the frequency as experience indicates. Verify voltmeter relay set points initially and each time the set point is changed. Also, indicate the reason(s) for the change. Log the date, time, location, a detailed description, and suspected causes for all faults located and cleared from the system Schneider Electric All Rights Reserved 21

24 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 5 Inspection and Maintenance 06/2008 ENGLISH Section 5 Inspection and Maintenance DANGER HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E. This equipment must be installed and serviced only by qualified personnel. Perform such work only after reading and understanding all of the instructions contained in this bulletin. Turn off all power supplying this equipment before working on or inside equipment. Assume that all circuits are live until they have been completely de-energized, tested, locked out, and/or tagged out (per OSHA ). Pay particular attention to the design of the power system. Consider all sources of power, including the possibility of backfeeding. Always use a properly rated voltage sensing device to confirm power is off. Carefully inspect your work area and remove any tools and objects left inside the equipment. Replace all devices, doors, and covers before turning on power to this equipment. Failure to follow these instructions will result in death or serious injury. Refer to the applicable low voltage equipment instruction bulletin for inspection and maintenance procedures Schneider Electric All Rights Reserved

25 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 6 Nameplate Information Section 6 Nameplate Information The high resistance grounding system nameplate is located on the front of the installed equipment. When ordering renewal parts, include in the parts description the factory order number found on the nameplate. The following list of information is found on the nameplate: Factory order number (plant manufacturing number) Drawing number (electrical diagram by which unit was wired) Phase (number of phases) System voltage (480 or 600 V) System type (Wye or Delta) Hertz (50 60 Hz) Rated current (maximum) Total grounding resistance NEMA Type (1 or 3R) Instruction bulletin number ( x) ENGLISH Section 7 Accessory Equipment Portable Ground Current Detector The portable ground current detector (Figure 10) is used as an aid in troubleshooting. The detector assists the technician in tracing the fault to its origin. Features of the portable ground current detector include: A multi-range switch ( short). Jaw openings that can be made to encircle 3-1/2-, 4-1/2-, or 6-inch (89-, 114-, or 182-milllimeter) conductors. Single-phase and three-phase system operations. A closed magnetic core to minimize the effects of stray fields. At least one portable detector should be available at the installation site. Figure 10: Ground Detector with Case Schneider Electric All Rights Reserved 23

26 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 8 Installation and Maintenance Logs 06/2008 ENGLISH Section 8 Installation and Maintenance Logs Table 2: System Initial Installation Charging Current (Amperage) Date Time I a I b I c R (Ohms) Voltmeter Reading (Volts) Table 3: Voltmeter Readings Date Time Volts Schneider Electric All Rights Reserved

27 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 8 Installation and Maintenance Logs Table 4: Voltmeter Relay Set Points Initial Set Point Set Point Change Date Time Volts Date Time Volts Reasons for Change ENGLISH Schneider Electric All Rights Reserved 25

28 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Section 8 Installation and Maintenance Logs 06/2008 Table 5: System Faults ENGLISH Date Time Location of Fault Description Suspected Causes Schneider Electric All Rights Reserved

29 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources 06/2008 Section 8 Installation and Maintenance Logs Table 6: Maintenance Log Date Description ENGLISH Schneider Electric All Rights Reserved 27

30 High Resistance Ground Unit for Use on 480 and 600 Volt Wye and Delta-Connected Sources Instruction Bulletin Schneider Electric USA 8821 Garners Ferry Road Hopkins, SC USA SquareD ( ) Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. No responsibility is assumed by Schneider Electric for any consequences arising out of the use of this material Schneider Electric All Rights Reserved Replaces , 08/ /2008

31 Sistema de resistencias de puesta a tierra Para su uso en sistemas de 50 ó 60 Hz con fuentes conectadas en estrella o delta de 480 y 600 V Clase 6036 Boletín de instrucciones Conservar para uso futuro.

32 ESPAÑOL CATEGORÍAS DE RIESGOS Y SÍMBOLOS ESPECIALES Asegúrese de leer detenidamente estas instrucciones y realice una inspección visual del equipo para familiarizarse con él antes de instalarlo, hacerlo funcionar o prestarle servicio de mantenimiento. Los siguientes mensajes especiales pueden aparecer en este boletín o en el equipo para advertirle sobre peligros potenciales o llamar su atención sobre cierta información que clarifica o simplifica un procedimiento. La adición de cualquiera de estos símbolos a una etiqueta de seguridad de Peligro o Advertencia indica la existencia de un peligro eléctrico que podrá causar lesiones personales si no se observan las instrucciones. Este es el símbolo de alerta de seguridad. Se usa para avisar sobre peligros potenciales de lesiones. Respete todos los mensajes de seguridad con este símbolo para evitar posibles lesiones o la muerte. PELIGRO PELIGRO indica una situación de peligro inminente que, si no se evita, podrá causar la muerte o lesiones serias. ADVERTENCIA ADVERTENCIA indica una situación potencialmente peligrosa que, si no se evita, puede causar la muerte o lesiones serias. PRECAUCIÓN PRECAUCIÓN indica una situación potencialmente peligrosa que, si no se evita, puede causar lesiones menores o moderadas. PRECAUCIÓN PRECAUCIÓN cuando se usa sin el símbolo de alerta de seguridad, indica una situación potencialmente peligrosa que, si no se evita, puede causar daño a la propiedad. Proporciona información adicional para clarificar o simplificar un procedimiento. OBSERVE QUE Solamente el personal especializado deberá instalar, hacer funcionar y prestar servicios de mantenimiento al equipo eléctrico. Schneider Electric no asume responsabilidad alguna por las consecuencias emergentes de la utilización de este material.

33 Sistema de resistencias de puesta a tierra, con fuentes conectadas en estrella o delta de 480 y 600 V 06/2008 Contenido CONTENIDO Sección 1 Introducción... 5 Sección 2 Precauciones de seguridad... 7 Sección 3 Recibo, manejo, almacenamiento e instalación... 8 Recibo... 8 Manejo... 8 Almacenamiento... 8 Instalación... 8 Sección 4 Típico sistema de resistencias de puesta a tierra... 8 Sistemas de baja tensión... 8 Transformador de alimentación de control (TAC)... 8 Neutro derivado... 8 Material del gabinete y resistencia... 9 Módulo de resistencia... 9 Gabinete del equipo... 9 Principios de funcionamiento Sistemas no puestos a tierra Puesta a tierra Circuito localizador de falla por impulsos Detección de puesta a tierra y alarma Detector de la corriente de tierra Corriente de carga capacitiva del sistema Selección del valor de la resistencia de puesta a tierra y conexiones 12 Diagramas de circuito de resistencia Componentes montados en la puerta Alarma de cuerno Ampérmetro Luz roja Luz verde Luz ámbar Botón de silenciamiento Selector Restablecimiento/Manual/Auto Selector "Normal/Impulso" Botón de prueba Voltímetro Componentes internos Procedimientos de puesta en marcha Diagramas del sistema de RPT Prueba del sistema de detección de tierra Uso del sistema bajo una condición de conexión a tierra real Verificación del sistema de alimentación Registros Instalación inicial del sistema Lecturas de voltímetro Puntos de ajuste del voltímetro Averías del sistema Sección 5 Inspección y servicios de mantenimiento Sección 6 Información en la placa de datos Sección 7 Accesorios del equipo Detector portátil de corriente de tierra Sección 8 Registros de instalación y servicios de mantenimiento ESPAÑOL Schneider Electric Reservados todos los derechos 3

34 Sistema de resistencias de puesta a tierra, con fuentes conectadas en estrella o delta de 480 y 600 V Lista de figuras y tables 06/2008 ESPAÑOL LISTA DE FIGURAS Figura 1: Diagramas de los sistemas en estrella y delta... 6 Figura 2: Configuración de neutro derivado... 9 Figura 3: Módulo de resistencia típico... 9 Figura 4: Detector de la corriente de tierra Figura 5: Diagramas de circuito de resistencia Figura 6: Ubicación de los componentes en la puerta Figura 7: Componentes internos Figura 8: Sistema de resistencias de puesta a tierra típicamente usado en sistemas en entrella Figura 9: Sistema de resistencias de puesta a tierra típicamente usado en sistemas en delta Figura 10: Detector de tierra con estuche LISTA DE TABLAS Tabla 1: Tabla de conexiones de las resistenciass Tabla 2: Instalación inicial del sistema Tabla 3: Lecturas del voltímetro Tabla 4: Puntos de ajuste del voltímetro Tabla 5: Averías del sistema Tabla 6: Registro cronológico de servicios de mantenimiento Schneider Electric Reservados todos los derechos

35 Sistema de resistencias de puesta a tierra, con fuentes conectadas en estrella o delta de 480 y 600 V 06/2008 Sección 1 Introducción Sección 1 Introducción Este boletín contiene información sobre la teoría así como instrucciones de funcionamiento y servicios de mantenimiento de los sistemas resistencias de puesta a tierra, fabricados por Schneider Electric. Este equipo proporciona un circuito de puesta a tierra para los sistemas de alimentación no conectados a tierra. Según las opciones seleccionadas, el equipo de puesta a tierra ofrece las siguientes funciones: Proporciona estabilidad al sistema y evita sobretensiones amortiguando las oscilaciones de alta frecuencia provocadas por fallas a tierra u otras distorsiones del sistema. Proporciona una manera de detectar y enviar una advertencia acerca de la primera falla a tierra que se produce en el sistema. Proporciona un medio de supervisar la condición de la tensión del sistema en relación con el potencial a tierra a través de mediciones de tensión. En caso de producirse una falla de línea a tierra, éste proporciona la manera de emitir impulsos a la corriente de falla a tierra de manera que ésta pueda ser rastreada con un detector portátil. Permite al sistema continuar su funcionamiento con una sola falla de línea a tierra presente. Estas funciones se pueden lograr ajustando la puesta a tierra del neutro del sistema de manera que las corrientes de falla a tierra sean un poco más altas que las corrientes de carga capacitiva natural de los sistemas no puestos a tierra. Al seleccionar las opciones apropiadas, el equipo de puesta a tierra es adecuado para sistemas no puestos a tierra configurados en delta o en estrella con corrientes nominales de 480 y 600 volts. Vea la figura 1 en la página 6. Los circuitos de control típicamente funcionan en 120 V~ (c.a.). ESPAÑOL Esta guía trata sobre varios usos de aplicación del equipo de puesta a tierra. Las ilustraciones y procedimientos son de carácter general. Su equipo puede ser diferente al que se muestra en la página 6. Consulte los dibujos de fábrica incluidos con el equipo de baja tensión. Las descripciones y especificaciones contenidas en esta guía fueron puestas en práctica en el momento en que se aprobó su impresión. Schneider Electric se reserva el derecho de dejar de fabricar ciertos modelos en cualquier momento, así como de realizar cambios a las especificaciones o diseño, sin previo aviso o contraer obligaciones. El equipo descrito aquí puede o no ser identificado como estándar u opcional. Si los procedimientos descritos en este documento no producen los resultados deseados durante la prueba, inspección o instalación del equipo, y no es posible determinar la causa de inmediato, póngase en contacto con el Centro de servicios en campo Square D llamando al (en EUA) o al SCHNEIDER ( ) / (en México) Schneider Electric Reservados todos los derechos 5