Transformer testeris a sensor used in power systems for measuring instruments,relay protectionand other secondary equipment to obtain information from the primary electrical circuit.
1.Voltage transformerconfiguration
(1) Busbar. Except for the bypass busbar, generally both the working and standby busbars are equipped with a set of voltage transformers for synchronization, measuring instruments, and protection devices.
(2) Line. For transmission lines of 35kV and above, when the opposite end has a power source, a single-phase voltage transformer is installed to monitor whether the line has voltage, for synchronization, and to set up reclosing.
(3) Generator. Generally, 2 to 3 sets of voltage transformers are installed. One set is for the automatic voltage regulator excitation device. Another set is for measuring instruments, synchronization, and protection devices.
(4) Transformer. On the low-voltage side of the transformer, sometimes a set of voltage transformers is installed to meet the requirements of synchronization or relay protection.
2.Current transformerconfiguration
(1) To meet the needs of measuring and protection devices, current transformers are installed in circuits such as generators, transformers, outgoing lines, busbar sections, bus coupler breakers, and bypass breakers. For systems with directly grounded neutral point, they are generally configured in three phases; for systems with non-directly grounded neutral point, they are configured in two or three phases according to specific conditions.
(2) The installation location of protective current transformers is set to eliminate the dead zone of the main protection device as much as possible.
(3) To prevent busbar faults caused by flashover of current transformer bushings, current transformers are usually arranged on the outgoing line side of the circuit breaker or on the transformer side, that is, as far as possible not to install current transformers close to the busbar side.
(4) To reduce the damage to the generator caused by internal faults, the current transformer used for automatic voltage regulator excitation device should be arranged on the outgoing line side of the generator stator winding. To facilitate analysis and to detect internal faults before the generator is connected to the system, the current transformer for measuring instruments should be installed on the neutral point side of the generator.
