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

1. Line Expansion and Renovation

Use the HTA-3300 Three-phase Digital Intelligent High-current Source to inject current directly on both sides of the current transformer (CT) of the expanded and renovated bay (for GIS equipment, current injection shall be performed via the earthing switch).

Take the voltage from the busbar voltage transformer (VT) terminal box or adjacent VT terminal box as the reference, apply the operating voltage to the protection device.

Simultaneously generate primary three-phase load current (0~300A, with adjustable amplitude and phase) that maintains a specific phase angle relative to the reference voltage, and inject the current through the CT. The current is then converted into secondary current and input into the protection device to verify the vector correctness of the line protection.

If the line expansion and renovation project is carried out synchronously at Substations A and B, two HTA-3300 devices shall be used at the two substations with time synchronization enabled. The test devices are respectively used to simulate primary load current flowing through the CTs, so as to verify the vector correctness of the line optical fiber differential protection.

For busbar protection vector check, the check can be completed by adopting the busbar protection wheel withdrawal method combined with relevant branch information.

2. Transformer Expansion and Renovation

For newly added transformers or renovation of transformer primary and secondary circuits, the HTB-8000 Large Transformer Primary Current Injection Test Device can be used for 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. This device enables a complete check of all primary and 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.

For tests that do not require current injection on transformer bushing CTs, two HTA-3300 devices can be used for synchronous current injection on both sides of the main transformer. External reference voltage can be used as the reference to check the single-side vector, or differential current can be used for vector check on both sides.

3. Busbar Expansion and Renovation

For projects involving the addition of a new busbar, the HTA-3300 series current injection method can be adopted to verify the vector correctness of the newly added bays and busbar protection.

The device takes a reference voltage and synchronously outputs 0-300A current to the primary side of the CT of a branch on the new busbar, with the current flowing out from the outgoing line side of another bay on the new busbar.

Through switch operation, the through short-circuit test of all branch bays of the busbar can be completed, realizing the vector check of the newly added bays and busbar protection.

This scheme is particularly suitable for newly added bays in projects such as high-speed railway traction substations, power plant step-up substations, and new energy terminal substations. In such sites, it is difficult to organize minimum load current, making vector check tests challenging. Unclear protection device direction for a long time may lead to maloperation or refusal to operate, and even affect normally operating bays. This scheme can effectively solve the above problems, ensure the one-time power transmission success rate, and improve the reliability of power grid operation.