Test Item: Phase Sequence, Phase and Polarity Verification of 220kV Lines

Test Equipment: HTA-3300 Three-phase Digital Intelligent High-current Source, HTV-6000 Three-phase Digital Intelligent High-voltage Source, YD-300 Wireless Telemetry Voltmeter-Ammeter Phase Indicator

01 Pre-test Preparation

Disconnect the disconnecting link between the line and the busbar, the earthing switch and circuit breaker of the line.

Ensure the secondary side of PT is not short-circuited and the secondary side of CT is not open-circuited.

Disconnect the power supply air switches of the voltage source and current source.

Ensure no personnel are working in the bay before starting the device.

02 Test Wiring

Current Source Connection: Connect the three-phase current wires of the current source to the incoming side of the primary CT, and the black wire to the outgoing side (the output value after reversal will be displayed as reverse polarity).

Secondary Measurement Connection: Clamp the wireless remote control current test leads between the secondary windings to be tested (secondary values can also be read on the protection device). Ensure the direction of the measurement leads matches the current flow in the winding, and insert the secondary test leads into the corresponding phase input ports of the remote control.

Voltage Source Connection: Connect the HTV-6000 to the booster box using an aviation plug cable, then connect the voltage wires to the primary side of the PT, paying attention to the direction of incoming and outgoing lines. Connect the secondary side of the PT to the remote control by inserting into the corresponding voltage measurement ports for secondary voltage measurement (values can also be read on the protection device).

△ Device Wiring Diagram

△ Three-phase Voltage/Current Source to Primary Equipment Wiring

△ Measuring Secondary Current in Secondary Circuit

Voltage Injection Path: Connect the HTV-6000 Three-phase Digital Intelligent High-voltage Source to the 220kV side of Main Transformer #4, at the upper end of switch 2308 (which is kept open). Close circuit breaker 230 and switch 2301 to apply voltage to 220kV Bus 1. Close the switch of PT Hu-01 to allow voltage to pass through the bus PT, so secondary voltage values can be checked on the protection device.

Current Injection Path: Connect the HTA-3300 Three-phase Digital Intelligent High-current Source to the storage line, at the upper end of switch 2298. Close switches 2298, 229 and 2301 to inject current into 220kV Bus 2. For testing the 220kV bay of Main Transformer #3, close switches 2268, 226 and 2262 to let current flow from the storage line to the bay, forming a loop. Secondary current values for this bay can then be checked on the protection device.

Remote Control Setup: Connect the YD-300 Wireless Telemetry Voltmeter-Ammeter Phase Indicator to the voltage and current sources, and output corresponding positive-sequence values to verify the phase sequence, phase and polarity of the line. When verifying other bays, there is no need to change the wiring between the devices and the bays; simply operate the circuit breakers of the target bay to enable or disable the test (e.g., for Main Transformer #2, open switches 2268, 226, 2262 and close 2248, 224, 2242).

Note: The primary circuits for voltage and current injection must not be connected together, as this will cause a fault. Normally, voltage is applied to one busbar and current to another.

△ Primary Circuit Diagram

03 Parameter Settings

Set the operating mode of the current and voltage sources to Remote Control Mode, then use the YD-300 to search for and connect to the devices.

After connection, set the output amplitude and phase. The phase is typically positive-sequence, i.e., phases A, B, C are 0°, 240°, 120° respectively. The amplitude should be set based on the CT/PT ratio, ideally resulting in integer secondary sampling values.

Return to the YD-300 app main interface and tap Start to control the connected devices to begin output.

Once running, compare the values displayed on the YD-300 with those on the source devices to verify normal output.

Verification Steps:

Phase Correspondence Check: Apply unbalanced three-phase voltage and current, then check that the secondary sampling values for phases A, B, C correspond correctly.

Ratio Verification: Calculate the CT/PT ratios and compare them with values read from the protection device to confirm normal operation.

Polarity Verification: Use phase values to check polarity. A 180° phase deviation indicates reverse polarity.

△ Collected Value Display

△ Protection Device Readings

Note: Since the secondary voltage is taken from the bus PT, the secondary voltage values are the same for all bays. Minor phase deviations due to interference from unbalanced three-phase injection do not affect polarity judgment.

04 Test Results

After the HTA-3300 and HTV-6000 were running normally, currents of 60A, 120A and 180A were applied to phases A, B and C respectively. By checking the amplitude and phase of the secondary values collected by the PT and CT on the protection device, it was confirmed that the three phases were correctly matched.PT Ratio: 220:0.1  CT Ratio: 1200:1

The calculated CT and PT ratios were found to be essentially consistent with the actual values. When the PT and CT polarities were normal, the currents IA4, IB4, IC4 flowed from the busbar to the line bay, and the secondary output phase was the same as the primary input phase. Positive-sequence correspondence confirmed positive polarity, indicating the line polarity was correct.