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Case Practice | Load Simulation Relay Protection Vector Checking for 500kV Substation

Release Date: June 21, 2024   Wuhan Haomai Electric Power Automation Co., Ltd.

Test Equipment: HTA-3300 Three-phase Digital Intelligent High-current Source, HTV-6000 Three-phase Digital Intelligent High-voltage Source, YD-300E Wireless Remote Control Host

Pre-test Inspection: No line testing work is in progress on site; no short circuit exists on the PT secondary side; no open circuit exists on the CT secondary side; power supply access is available.

Test Wiring

△ Current Source Wiring Diagram of Main Transformer Bay

Voltage Source Wiring

Open the PT secondary terminal box, connect the secondary wiring of the HTV-6000 Three-phase Digital Intelligent High-voltage Source to the root of the PT secondary side for quantity application, and disconnect the secondary wiring to prevent reverse power transmission, so as to verify the correctness of the entire PT secondary circuit.

△ Three-phase Voltage Application Position of Voltage Transformer

Current Source Wiring

Remove the grounding connection point of the grounding switch (506117 switch) in the 500kV 5061 main transformer bay. Before the test, disconnect the grounding connection points of other current-carrying circuits to ensure that only the grounding connection point of the grounding switch (506127 switch) in the 500kV #4 main transformer bay is retained. Connect the cables to the Phase A, B and C output terminals of the HTA-3300 Three-phase Digital Intelligent High-current Source in sequence from the lead at the removal point (506117 switch), and connect the N wire of the high-current source to the grounding copper bar (the red lines in the figure below represent the flow direction of the three-phase current circuit, with the states of switches and disconnecting switches shown as per the diagram). Switches 506117, 5061 and 506127 are in closed position; all other disconnecting switches connected to the 500kV bus are open; all other disconnecting switches and grounding switches are in open position.

△ Current Source Wiring Diagram

△ Three-phase Current Application Position of 5061 Main Transformer Bay

Parameter Settings

Set the operation mode of the current source and voltage source to remote control mode. Use the YD-300E Wireless Remote Control Host to search for the corresponding equipment. After connection, set the output amplitude and angle. After the settings are completed, return to the remote control main interface and click "Start" to control the connected devices for output.

△ Application Result of Differential Current Balance

When applying voltage with the voltage source, connect the Phase A, B and C secondary voltage output ports to different secondary windings of the Phase A PT, and connect the protection winding to the C output port. The main transformer protection device displays that the amplitude of IA is 0.039A with an angle of 6°, the amplitude of IB is 0.038A with an angle of 246°, the amplitude of IC is 0.039A with an angle of 124°, UA is 29.5V, and the displayed values of UB and UC are drift values with no reference significance.

Test Result Analysis

The CT ratio on the main transformer side is 5000:1. When a current of 200A is applied on the primary side, the displayed current on the secondary side should be 0.04A. Since the current injection direction is from the bus to the transformer during current source wiring, the results displayed on the protection device should be consistent with the applied quantity. It can be seen from the results in the above figure that the vector checking of this transformer bay is correct.