During the installation and commissioning of CTs and PTs in newly-built and renovated substations, potential issues may arise. These issues may not be detected when the primary team or secondary team conducts separate inspections, but will only surface when primary and secondary systems are coordinated during commissioning. Therefore, before a substation is put into operation, it is necessary to perform phasor and polarity checking with the coordination of primary and secondary systems to identify and resolve problems in a timely manner.

To address this need, Wuhan Haomai has independently developed the HTA/HTV wireless remote-controlled digital intelligent current/voltage sources. These devices can simulate primary-side load operation, and cooperate with the wireless remote control host to inject quantities on the primary side and conduct measurements on the secondary side. This enables the completion of ratio, phasor and polarity tests for the entire primary and secondary circuits, while also identifying faults in these circuits and eliminating potential risks prior to substation commissioning.

Recently, a 220kV substation of a power supply company under the State Grid, which was pending commissioning, adopted the HTA-3300 Three-phase Digital Intelligent High-current Source combined with the HTV-6000 Three-phase Digital Intelligent High-voltage Source to complete phasor checking and polarity verification for the GIS equipment in the substation.

1. Substation Conditions and Wiring Method

All CTs in the GIS substation are in an enclosed state. For wiring, connection terminals exposed on the grounding terminals are selected. The ground bar is disconnected, and the HTA-3300 is connected to the CT terminals. On the other side of the CT, the grounding disconnecting switch is closed, and the N pole of the HTA-3300 is connected to the ground bar to form a current loop.

Since the newly-built substation had not yet implemented relevant voltage boosting measures, and considering the potential safety hazards of sudden voltage boosting, secondary voltage was directly applied to the secondary circuit. One path of the voltage was connected to the wireless remote control host as the voltage reference, so that the current source could output with the voltage phase as the reference to complete phasor verification.

2. Quantity Injection and Result Checking

After completing the wiring of the primary and secondary circuits, the wireless remote control host was used to collect the voltage reference and control the HTA-3300 to output high current. A suitable current was output according to the CT ratio, and the amplitude and phase of the secondary-side current were measured by using the volt-ampere phase measurement function of the wireless remote control host.

After completing the test for a single bay, the test was stopped, the grounding disconnecting switch of this bay was opened, and the circuit breaker was closed. The same operation was performed for another bay, allowing the current to flow from the CT of this bay to the busbar and then to the next bay, thus completing the inter-bay phasor test.

3. Test Results and Analysis

The CT ratio was verified to be correct based on the amplitude measured by the wireless remote control host, and the CT installation direction was confirmed to be correct according to the phase angle. The entire test was calibrated by cross-checking the values displayed on the protection device.

In this project, Wuhan Haomai cooperated with on-site personnel of the power supply company to complete the verification of the primary and secondary circuits in the substation, and the entire test process was highly successful. The user stated that this set of equipment solved the problems encountered in substation operations based on actual demands, and gave unanimous praise to the equipment's practicability, stability and advanced performance.