Relay protection is critical equipment for the safe and stable operation of power systems. Conducting a vector check after replacing relay protection devices can ensure that the new equipment responds accurately and promptly to power grid faults. This prevents power accidents caused by maloperation or failure to operate of protection devices due to incorrect, wrong, or missing connections of secondary cables.

1. Busbar Differential Protection Replacement

During the replacement of busbar differential protection, the primary equipment remains in operation. After the replacement is completed:

For in-service branches that keep running without power outage, the load current of the branch can be directly used to check the wiring and polarity.

For standby branches, with the switch and disconnecting link in the open state, the HTA-3300 Three-phase Digital Intelligent High-current Source can be used to inject current into the primary side of the CT of the branch, simulating load current to check the wiring and polarity of the secondary circuit.

The HTA-3300 can output three-phase current ranging from 0 to 300A. The output phase can be synchronized with the running voltage UA of the PT. The amplitude and phase of each of the three phases are independently adjustable. It can also simulate zero-sequence and negative-sequence currents to check the N-line, thus completing a full inspection of the standby branches.

2. Transformer Protection Replacement

Transformer protection is usually replaced during power outages, and the HTB-8000 Large Transformer Primary Current Injection Test Device can be used to complete the secondary vector check.

The HTB-8000 offsets the magnetizing inductive reactance of the transformer through series capacitor compensation. It uses a 380V/220V power supply to inject 100A current into the primary winding (outside the CT) of the medium-voltage (or high-voltage) Y-side of the transformer, while other sides are short-circuited separately (outside the CT). Primary current flows through the CTs on all sides of the transformer, and the secondary current generated in the CT secondary circuit can be used for the vector check of transformer protection.

Each phase current can be adjusted independently, and can also form zero-sequence current for N-line check. The device enables a complete check of all secondary circuits of the transformer, and is especially suitable for converter transformers and replacement of main transformer protection for voltage classes of 500kV and above. It can conduct current injection on transformer bushing CTs, and simultaneously verify the wiring correctness of transformer longitudinal differential protection, phase differential protection, split-side differential protection, and low-voltage side zone differential protection circuits, thus completing a full vector check.

3. Line Protection Replacement

For line bays in a double-busbar system where protection devices are replaced during power outages, the HTA-3300 Three-phase Digital Intelligent High-current Source can be adopted to output 0–300A current to the primary side of the CT. This current is synchronized with the secondary running voltages UA1 and UA2 of the PTs of the two busbar sections respectively, simulating the load current when the line bay is connected to each of the two busbar sections. The simulated current is used for the vector check of the secondary circuit of the bay. It can also simulate and output zero-sequence current for N-line check.

Conducting relay protection vector checks after device replacement is a technical requirement that should be followed in the design and operation of power systems. It ensures that the replaced relay protection devices comply with technical specifications, which is of great significance for safeguarding the safe, stable, and reliable operation of power systems.