The vector and polarity checking of a photovoltaic booster station is mainly to detect the phase relationship between voltage and current, verify whether the phase relationship between voltage and current meets expectations, ensure the correct connection and operation of power equipment, and avoid adverse impacts on the power grid during grid-connected operation. The following is a partial primary wiring diagram of a 110kV photovoltaic booster station. It is necessary to conduct vector verification on bays 401 and 402 before power transmission, and connect them to the 110kV line for grid connection only after confirming correctness.

△ Partial Primary Wiring Diagram

1. Test Method

△ Two Main Transformer Bays and Current Injection Direction

During the test, on the #1 main transformer side, it is necessary to open the 4011 disconnecting switch and 40130 grounding switch, close the 40140 grounding switch, 401 circuit breaker and 4013 disconnecting switch, and disconnect the 40110 grounding switch. On the #2 main transformer side, it is necessary to open the 4021 disconnecting switch and 40230 grounding switch, close the 40240 grounding switch, 402 circuit breaker, 4023 disconnecting switch and 40210 grounding switch.The HTA-3300 Three-phase Digital Intelligent High-current Source injects current from the 40110 grounding switch on the #1 main transformer side, flows through the CT of bay 401, then flows into the CT of bay 402, and finally flows into the ground from the 40210 grounding switch on the #2 main transformer side to form a current loop.The secondary voltage of the HTV-6000 Three-phase Digital Intelligent High-voltage Source is connected to the PT terminal box of bay 401, led to the 401 line protection device, and connected in parallel to the 402 line protection device through cables. The YD-300E Intelligent Wireless Remote Control Host for Current and Voltage Sources is used to realize synchronous output of current and voltage.

To check the absolute phase angle of the current loop, it is necessary to apply secondary voltage. The rated voltage is directly output to the protection device through the HTV-6000. Taking the phase A bus voltage as the reference, the CT secondary amplitude and angle can be viewed on the protection device of each bay, and the correctness of the vector polarity can be judged according to the definition of the CT polarity terminal.

2. Test Wiring

Since the 110kV part of this station is GIS equipment, the selection of the current injection point should consider sufficient space to ensure a sufficient safety distance between primary equipment and personnel during the test, and a three-phase power supply meeting the power supply requirements of the test equipment should be available nearby. After investigation, it is determined to conduct current injection at bay 401.

Current Source Wiring

Wiring Method: Disconnect the 40110 grounding switch at bay 401, connect the phase A/B/C test wires of the three-phase current source to the corresponding phase A/B/C terminals as the current injection point. After passing through the test loop, the current flows into the ground from the 40210 grounding switch at bay 402.

Voltage Source Wiring

Wiring Method: Disconnect the slider of the protection winding in the PT terminal box of bay 401 (to prevent voltage from being transmitted to the primary side of the PT), and connect the three-phase secondary voltage of the voltage source to the terminals of the protection voltage winding. The secondary side of the voltage PT terminal box to protection #1 is connected in parallel to protection #2 as the reference voltage, which is connected to the YD-300E.

3. Test Process

The ratio of the CT protection winding of bay 401 in the booster station is 1000/5, and the ratio of the CT protection winding of bay 402 is 800/5. The CT windings of the two bays are inconsistent, and the protection device will perform ratio coefficient compensation to calculate the differential current value.After completing the above wiring, check whether the power supply is normal, power on the current source and voltage source, first output appropriate unbalanced primary current and secondary voltage values separately in single-machine mode, check the sampling values on the protection device, and verify whether the phase sequence is correct.

4. Test Results

After the current is boosted, check the current of each bay side on the protection panel.

△ Device Output Values and Protection Sampling Values

Multiple Test Data

1. Set the current output to 80A, voltage to 50V, and output with a leading current angle of 0°.

2. Set the current output to 160A, voltage to 50V, and output with a leading current angle of 45°.

The above data is consistent with the data measured by the YD-300E at the CT terminal box. Since the primary current flows from P1 to P2 in bay #1, the theoretical value of Ang(U-I) should be 0°. The primary current flows from P2 to P1 in bay #2, so the theoretical value of Ang(U-I) should be 180°. The actually measured data is consistent with the theoretical value. Therefore, it can be concluded that the CT vector polarity of the two bays is correct, and they can be connected to the 110kV line for grid connection.