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I-Gard SIGMA 3 Manual

Ground fault relay
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SIGMA 3
C-EG44EM, February 2021

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Summary of Contents for I-Gard SIGMA 3

  • Page 1 SIGMA 3 C-EG44EM, February 2021...
  • Page 2 ABOUT I-GARD I-Gard’s commitment to electrical safety provides both industrial and commercial customers with the products needed to protect their electrical equipment and the people that operate them. As the only electrical-safety focused company whose product portfolio includes neutral grounding resistors, high-resistance grounding systems and optical arc mitigation, we take pride in our technologies that reduce the frequency and impact of electrical hazards, such as arc flash and ground faults.

  • Page 3: Table Of Contents

    Table 8.6: MODBUS Register Format Conventions Table 10.1 NGR Test Values FIGURES Figure 3.1: Sigma 3 Typical System Diagram (HRG System) Figure 3.2: Sigma 3 Typical System Diagram (LRG System) Figure 3.3: The Creation of a Pulse Signature by Cycling the Let-Through Current Under Various Arrangements Figure 6.1: Sigma 3 Dip Switch Array...

  • Page 4: Introduction

    NGR current to the relay’s set let-through current. The Sigma 3 monitor relay is designed to operate with a TxA or Rx-yA zero sequence current sensor, an NGRS# sensing resistor with NGRX filter, and an NGR sized to limit ground fault current.
  • Page 5 For High Resistance Grounded Systems (HRG) a single high frequency injection channel (HF1) is employed. See Figure 3.1 below for the typical system with the Sigma 3 connections. For Low Resistance Grounded Systems (LRG) two high frequency injection channels (HF1 and HF2) are employed. See Figure 3.2 below for the typical system with the Sigma 3 connections.
  • Page 6 GND FLT form-C contact energizes, and the trip relays energize. The Sigma 3’s NGR let-through current setting is set by DIP switch to match the rating of the NGR. The trip level is DIP switch selectable as a percentage of the NGR let-through current setting and can be set as: 5%, 10%, 15%, 20%, 25%, 30%, 40%, and 50%.
  • Page 7 3.3 NGR Monitoring The Sigma 3 monitor relay also monitors the health of the NGR to ensure that it does not become open or short circuit. If the Sigma 3 determines that the NGR is not healthy the NGR FLT LED illuminates, the NGR FLT form-C contact energizes, and the trip relays energize.

  • Page 8: Trip Relay And Auxiliary Fault Relays

    All relays are electrically held, i.e. when control power is off the relays are always in the de-energized state. The de- energized states are shown on the front of the Sigma 3. Note that this is irrespective of the trip relay operating mode.
  • Page 9 The Green PWR LED will turn ON when control power is applied to the Sigma 3 and the relay is operating normally. The Green PWR LED will intermittently flash if control power is applied to the Sigma 3 but the relay is not operating correctly due to a malfunction in the microprocessor circuit.

  • Page 10: Settings

    6.1 Trip Relay Operating Modes The trip relay operating settings can be set with DIP switch 1. The Sigma 3 can be set for a shunt trip operating mode (not failsafe) or an undervoltage trip operating mode (failsafe) operation with the trip relay operating mode dip switch.
  • Page 11 The trip relay will energize (no-trip) if the Sigma 3 is reset through a local or remote reset. When reset, the Sigma 3 will resume monitoring of the system and, if a fault remains on the system, will detect the fault and will re-trip, de- energizing the trip relay.
  • Page 12 The NGR let-through current settings in Table 6.6 are intended to show that the Sigma monitor relay can be config- ured for let-through currents ranging from 1 Ampere through 4 Amperes using a standard I-Gard TxA ZSCS with the conductor carrying the NGR current wrapped through the CT’s primary window 10 times to create a primary winding of 10 turns.
  • Page 13 Trip Memory On/Off Dip Switch Setting TRIP MEMORY ON Control voltage off after trip: When control voltage restored Trip and Aux relays idle* then immediately re-trip (within 2 seconds). TRIP MEMORY OFF Control voltage off after trip: When control voltage restored DOWN Trip and Aux relays idle* but do not immediately re-trip...
  • Page 14 1750 1850 1950 2050 2150 2250 2350 2450 2550 2650 2750 2850 2950 3050 3150 (U = Up, D = Down) Table 6.3: Ground Fault Trip Time Delay Settings Dip Switches #3-#4-#5-#6-#7 (left hand array) Ground Fault Trip Level (% of NGR Dip Switch Settings Let-Through Current) (U = Up, D = Down)
  • Page 15 NGR Let-Through Dip Switch Settings ZSCS Employed Current (Amps) TxA or Rx-yA w/10 Turns Through Primary TxA or Rx-yA w/10 Turns Through Primary TxA or Rx-yA w/10 Turns Through Primary TxA or Rx-yA w/10 Turns Through Primary TxA or Rx-yA TxA or Rx-yA TxA or Rx-yA TxA or Rx-yA...

  • Page 16: Use With Sigma3-Tdm Touchscreen Display Module

    7. USE WITH TOUCHSCREEN DISPLAY MODULE The Sigma 3 can be used with a touchscreen HMI called the Sigma3-TDM. The Sigma 3 is connected to the Sigma3- TDM using its MODBUS communication. The connection of the Sigma 3 to the Sigma3-TDM is shown in Figure 7.1.
  • Page 17 Figure 7.1: Sigma 3 to Sigma3-TDM Connection Diagram Navigate to the Settings page using the associated button on the home screen. The Settings page is shown in Figure 7.5 below. From here, the Sigma Settings page can be accessed. Select the system voltage (i.e. L-L voltage). Pulse frequency can be selected.
  • Page 18 Figure 7.3: Status Screen Figure 7.4: Event Log Page Figure 7.5: Settings Page...
  • Page 19 Figure 7.6: Sigma and Alarm Settings Page Figure 7.7: Pulse Contactor Settings Page Figure 7.8: Communications Settings Page...

  • Page 20: Modbus Communication

    The shield of the cable between nodes should not be continuously grounded but should be grounded at one end. The cable may be grounded at the Sigma 3 using the ground connection provided on termi- nal # 6.
  • Page 21 This document summarizes the format and function of these registers. The request from the master is always 8 bytes long and are as shown in the table below. In the MODBUS RTU system the Sigma 3 operates in a cli- ent/server communications model or master/slave communications model.
  • Page 22 There are times when the Sigma 3 relay processor will not be able to respond to a request since it is busy with other tasks and no response will be returned. For this reason it is recommended to request the maximum number of regis- ters used by the system in a single request.
  • Page 23 40008 nnnnH 40009 nnnnH 40010 nnnnH 40011 nnnnH 40012 nnnnH 40030 Relay status nnnnH 40012 40013 nnnnH 40031 NGR Status nnnnH 40013 40014 nnnnH 40015 nnnnH 40040 Internal measurement of the GF cur- nnnnH 40015 rent as measured by the CT 40016 nnnnH 40041...

  • Page 24: Installation

    0 or 1 Table 8.6: MODBUS Register Format Conventions 9. INSTALLATION 9.1 Sigma 3 9.9.1 Location The Sigma monitor relay should be located as close as possible to the system’s isolating device, circuit breaker or contactor.
  • Page 25 Sigma monitor relay. Refer to Figure 9.1. The I-Gard percentage ammeter is designed for use in this application. If a meter other than the I-Gard GM-AM1 is used, observe the polarity shown on the front panel and in Figure 9.1.
  • Page 26 9.3. NGRXS-## Sensing Resistor The NGRS-XX sensing resistor must be selected from those available from I-Gard and must be one that is designed for use in a system with a system voltage in which it will be installed. 9.3.1 Location The NGRS-XX sensing resistor should be mounted near the system transformer, along with the ZSCS and the NGR.

  • Page 27: Commissioning

    10. COMMISSIONING A general breakdown of commissioning of the Sigma 3 would involve the following: Review of installation and condition of unit Verification of connections Verification of settings Energization of Sigma 3 Functional Verifications: Test and Reset Pulsing Communication with the Sigma3-TDM...
  • Page 28 4.3 Locate potentiometer R84 as shown in the Figure 10.1 below. 4.4 With control power still provided to the Sigma3, adjust the potentiometer until the HF1 current is 19mA. Figure 10.1: Potentiometer to be used to Adjust HF1 Current 5. Offline Calibration Procedure 1.
  • Page 29 9. In this calibration mode, the DIP switches #1 to #10 represent the value of the NGR fault short-circuit tripping value as a binary number. Adjust DIP switches #1 to #10 by sequentially increasing the setting in the following manner: 9.1.
  • Page 30 Figure 10.2 (b): Example of DC Ammeter used in Calibration Procedure Figure 10.3: Partial Short on NGR when Performing Offline Calibration...
  • Page 31 6. Online Calibration Procedure Using Sigma3-TDM 1. Ensure the Sigma3-TDM is connected to the Sigma3 as shown in Figure 10.4 below, or refer to the installation section of C-EG44-EM. Figure 10.4: Sigma3 -TDM to Sigma3 connection 2. From the home page, navigate to SETTINGS -> SIGMA & ALARM SETTINGS and ensure that the system settings are correct for the application (see Figure 10.5 below).
  • Page 32 3. From the home page, navigate to SETTINGS -> SYSTEM CALIBRATION as shown below. Figure 10.6: Sigma3 Calibration Page 4. With the system in its stable normal operating conditions observe the value of “Conductance Measurement”. Note this value as CM (normal). 5.
  • Page 33 10.3 Warning Concerning Hi-Pot and Dielectric Testing of the System As the Sigma monitor relay, NGRS-XX sensing resistor and ZSCS have undergone and passed high-pot testing at the factory, field testing of the relay is unnecessary and may damage these components. For any high-pot tests or dielectric withstand tests on the system conducted in the field, the Sigma monitor relay, NGRS-XX sensing resistor and ZSCS must be prepared as described below to avoid damaging this equipment.

  • Page 34: Technical Specifications

    11. TECHNICAL SPECIFICATIONS Electrical Ratings: Control: 110-240VAC 5VA AC or 5W DC Range: -45% to + 10% (60-264V AC/DC) Output Relay Contacts: Main Trip Relay: Type: Form Z (NO and NC Pair) Rating: 10A @ 240VAC 10A @ 30VDC All relays are electrically held and are de-energized 1/2 HP @ 240VAC when control power if OFF.

  • Page 35: Catalogue Numbers

    Continuously rated, except when ground-fault tripping is provided; b) Monitored so as to de-energize the supply in less than 60s if the neutral-grounding device opens; and c) Connected as close as practical to the supply neutral. C-EG44EM SIGMA3 Phone: 905-673-1553 Fax: 905-673-8472 Toll Free: 1-888-737-4787 support@i-gard.com www.i-gard.com...

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