GE IS200EXAMG1B Exciter Attenuation Module

The IS200EXAMG1B is an Exciter Attenuation Module designed by General Electric (GE) for its EX2100™ and EX2100e™ Excitation Control Systems. This module is an important hardware revision within the EXAM series. Compared to the earlier G1A version, the G1B version adds a test relay function, enabling it to more comprehensively support the self-test functionality of the ground detection system, particularly in EX2100e regulator control applications. The IS200EXAMG1B module works in conjunction with the Exciter Ground Detector Module (EGDM) or the Auxiliary Interface Board (EAUX) to form a complete ground detection system, used to monitor the insulation condition of the generator field circuit to ground.

The IS200EXAMG1B module is mounted in the High Voltage Interface (HVI) module located in the auxiliary cabinet. Its primary function is to attenuate the high voltage from the field bus to a usable low-level signal for processing by the ground detection circuitry. In the EX2100 excitation control system, the IS200EXAMG1B connects to the Exciter Power Backplane (EPBP) via a single 9-pin cable, while the EGDM plugs into the EPBP through a 96-pin connector, P2. The EGDM controls the activation of ground tests and the selection of the master controller via a relay located in the EXAM.

In the EX2100e regulator control system, the IS200EXAMG1B interfaces with the EAUX board. The EAUX provides a ±50 V square wave signal to the EXAM and receives an analog feedback signal proportional to the ground current back from the EXAM. The EAUX provides two relay driver outputs to the EXAM: one for selecting the M1 or M2 redundant ground detector, and one for controlling the test relay on the IS200EXAMG1B, which can temporarily insert a ground resistance to test the ground detector function. This is the core upgrade of the G1B version compared to earlier versions.

When a ground test is activated, the bus voltage is distributed across attenuation resistors and sense resistors. The test can last up to 10 seconds. If a dead short to ground occurs on the bus, the entire bus voltage will appear across a single section of the attenuation resistors, and the system will generate a fault and shut down the exciter within 10 seconds.

The IS200EXAMG1B module has a simple and reliable design with no test points, fuses, or LED indicators. The module includes the following components:

• J2 Connector: 9-pin D-type connector for test signals, relay control, and leakage current.

• J1 Connector: 3-pin locking connector for the cable to the field flashing relay auxiliary contact.

• E1, E2 Stab-on Connectors: Connect the positive and negative field bus voltages.

• TB1 Terminal: Connection point for the EXAM board shield ground to the cabinet chassis ground.

• JP1, JP2, JP3 Jumpers: Used to configure the module for different PPT secondary voltage levels.

• Test Relay K2: Newly added test relay, controlled by EAUX, for ground detection function self-test.

  
  

II. Main Functions

The primary functions of the IS200EXAMG1B include, but are not limited to, the following:

1. High-Voltage Attenuation

The IS200EXAMG1B module uses an attenuation resistor network to reduce high voltages from the field bus (125 V dc to 1000 V dc) and the Power Potential Transformer (PPT) AC voltage (120 V ac rms to 1300 V ac rms) to low-level signals suitable for processing by the ground detection circuitry. The attenuation ratio is determined by the internal resistor network, ensuring safe output levels under both normal and fault conditions.

2. Ground Test Activation

When the EGDM or EAUX initiates a ground test, the IS200EXAMG1B module activates the corresponding relay based on control signals. In EX2100e applications, the test relay (K2) is controlled by the EAUX to temporarily insert a ground resistance, simulating a ground fault to verify the correctness of the ground detection function. The test voltage is a ±50 V square wave provided by the active master controller. The test can last up to 10 seconds.

3. Master Controller Selection

In redundant systems, the select relay (K1) within the IS200EXAMG1B module is controlled by the EGDM C board. It selects M1 or M2 as the active master controller. The relay's default state is de-energized, feeding back to the M1 controller; when energized, it feeds back to the M2 controller. This mechanism ensures that if one master controller fails, the ground detection function can still be performed by the other master.

4. Test Relay Function

The newly added test relay (K2) on the IS200EXAMG1B is a core upgrade compared to earlier versions. This relay, controlled by the EAUX, can temporarily insert a known ground resistance while the system is running, simulating a ground fault. By measuring the ground current and calculating the ground resistance at this time, the system can verify the correctness of the ground detection circuitry and algorithms, achieving a self-diagnostic function and enhancing system reliability and maintainability.

5. Fault Detection and Protection

If a dead short to ground occurs on the bus, the entire bus voltage appears across a single section of the attenuation resistors. The IS200EXAMG1B module and the EGDM/EAUX detect this abnormal condition and generate a fault signal within 10 seconds, triggering an exciter shutdown to protect equipment and personnel.

6. Signal Isolation and Transmission

The IS200EXAMG1B module receives the square wave test signal from the EGDM or EAUX via the J2 connector and returns the attenuated signal from across the sense resistor to the ground detection circuit. The J1 connector connects to the field flashing relay auxiliary contact, allowing the test signal to be removed during field flashing.

7. Configuration Flexibility

Three jumpers, JP1, JP2, and JP3, allow configuration of the IS200EXAMG1B module's filter capacitance based on the site's PPT voltage level, ensuring accurate measurements across different voltage ranges.

III. System Applications

1. Application in EX2100 Excitation Control System

In the EX2100 excitation control system, the IS200EXAMG1B works with the EGDM to form the ground detection system:

• High-Voltage Attenuation: Attenuates the high voltage from the field bus to low-level signals, sent to the EGDM via the EPBP backplane.

• Ground Test Execution: Based on control from the EGDM C board, activates the select relay, applying the ±50 V square wave test voltage to the sense resistor.

• Master Controller Selection: Uses the internal select relay to choose the active master controller between M1 and M2, ensuring redundant ground detection functionality.

• Fault Protection: Assists the system in triggering a shutdown within 10 seconds upon detecting a dead short to ground.

2. Application in EX2100e Excitation Control System

In the EX2100e regulator control system, the IS200EXAMG1B works with the EAUX or ERAX, where the G1B version's test relay function plays a crucial role:

• Signal Interface: Receives the ±50 V square wave test signal from the EAUX via the J2 connector and returns the sense resistor signal to the EAUX.

• Select Relay Control: The EAUX controls the select relay via J2 pin 8 to choose the M1 or M2 redundant ground detector.

• Test Relay Control: The EAUX controls the test relay (K2) via J2 pin 7, enabling temporary insertion of a ground resistance to simulate a ground fault, allowing self-test and verification of the ground detection function.

• Signal Removal During Flashing: Connects to the field flashing relay auxiliary contact via the J1 connector, removing the test signal during field flashing.

3. Self-Diagnostic Function

Thanks to the newly added test relay, the IS200EXAMG1B supports the self-diagnostic function of the ground detection system. The system can periodically or on-demand activate the test relay, simulating a ground resistance of a known value. By measuring the ground current and calculating the ground resistance value, it verifies the integrity and accuracy of the entire ground detection channel (including the EXAM attenuation network, EAUX acquisition circuit, and DSPX calculation logic). This significantly improves system maintainability and reliability.

4. Application in PGDM Standalone Ground Detection Product

The IS200EXAMG1B can also be used in the standalone PGDM ground detection product, working with the BPPB processor board, BFGD acquisition board, and BGTB terminal board to provide ground detection functionality similar to the EX2100 system.

5. Typical Application Scenarios

• Ground protection for synchronous generator excitation systems (requiring self-diagnostic function)

• Rotor ground monitoring for steam turbine generators (high reliability requirements)

• Insulation monitoring for hydro turbine generator field circuits

• Ground fault detection for gas turbine excitation systems

• Protection for industrial large motor excitation systems

  
  

IV. Detailed Interface Description

1. J2 Connector (Ground Detect Connector)

J2 is a 9-pin D-type connector (female) used for connection to the EPBP (EX2100) or directly to the EAUX/ERAX (EX2100e). Pin assignments are as follows:

2. J1 Connector

J1 is a 3-pin locking connector for connection to the field flashing relay auxiliary contact:

3. E1 and E2 Stab-on Connectors

4. TB1 Ground Terminal

TB1 is the connection point for the EXAM board shield ground to the cabinet chassis ground, ensuring effective shield grounding and reducing electromagnetic interference.

5. Relays K1 and K2

The IS200EXAMG1B module contains two internal relays:

• K1 (Select Relay): Used to select the active master controller (M1 or M2), controlled by EGDM C or EAUX.

• K2 (Test Relay): Newly added relay for ground detection self-test, controlled by EAUX only in EX2100e applications.

  
  

V. Configuration Jumpers

The IS200EXAMG1B module has three configuration jumpers, JP1, JP2, and JP3, used to select the appropriate filter capacitance based on the site's PPT voltage level.

JP1 and JP2

These two jumpers work together to select whether the PPT voltage is greater than 750 V rms:

JP3

JP3 independently selects whether the PPT voltage is greater than 375 V rms:

Note: Jumper settings must be configured according to the actual site PPT secondary voltage. Incorrect settings may lead to inaccurate measurements or module damage.

VI. Installation and Replacement

1. Mounting Location

The IS200EXAMG1B module is mounted on a Glastic® bracket inside the High Voltage Interface (HVI) module in the auxiliary cabinet. During installation, ensure the module is firmly seated and all connectors are correctly attached and tightened.

2. Replacement Procedure (EX2100 or EX2100e System)

Important Safety Warnings:

• The EXAM module is located in a high-voltage circuit. Power to the excitation system MUST be turned off before replacement. Follow the complete de-energizing procedures outlined in GEH-6631 (EX2100) or GEH-6780 (EX2100e). Adhere to all local Lock-out/Tag-out practices. Allow time for capacitors to discharge.

• Use safety test equipment designed for high voltages to confirm circuits are de-energized before touching them.

• Adhere to ESD (Electrostatic Discharge) precautions when handling the module. Wear a grounding strap and store the module in anti-static bags.

• The EXAM module does NOT support online replacement. Power must be off before replacement.

Replacement Steps:

1. Verify Power Off: Ensure the excitation system is completely de-energized.

2. Open Cabinet Door: Open the auxiliary cabinet door. Using high-voltage test equipment, verify that circuits are de-energized.

3. Label Cables: Verify all cables are correctly labeled according to the markings on the module for easy reconnection.

4. Disconnect Cables:

• Disconnect E1 and E2 stab-on connectors.

• Disconnect J1 and J2 connectors.

• Disconnect the ground wire from TB1.

5. Remove Old Module: Carefully unseat the module from the mounting pins and remove it from the Glastic® bracket.

6. Inspect New Module: Verify that the JP1-JP3 jumper settings on the new module match the original module.

7. Install New Module: Firmly seat the new module onto the Glastic® bracket.

8. Reconnect Cables: Reconnect all cables and the ground wire as labeled, and tighten connectors.

9. Restore Power: Close the cabinet door, restore power to the excitation system following procedures, and test operation.

3. Replacement Procedure in a PGDM Module

1. Verify Power Off: Ensure both the PGDM and the protected excitation equipment are completely de-energized.

2. Follow steps 2-8 above.