Capacitive voltage transformers also ensure suitable electrical insulation between high voltage and low voltage measuring equipment and are available with accessories for PLC transmission and Power Quality measurement. This LW8A Outdoor High Voltage SF6 Circuit Breaker With Good Quality constructed three phase measurement voltage transformer comes in 3 standard frame sizes and all standard voltages between 55 – 480 volts primary and 63.5 – 240 volts secondary.
This robust and compact constructed single phase measurement voltage transformer comes in 3 standard frame sizes and all standard voltages between 55 – 480 volts primary and 63.5 – 240 volts secondary. Instrument Transformers also have a range of medium voltage transformers, either epoxy resin cast or oil filled impregnated paper type, suitable for indoor and outdoor installation. Low voltage instrument type voltage transformers are configured as single phase measurement or single phase protection.
Voltage transformers type EGF are used in high voltage substations within the 245-550 kV range. Current transformers decrease high voltage currents to some reduced value and supply a handy method of properly checking the particular electric powered current moving within an AC transmission line utilizing a standard ammeter. Current transformers could be attached to the lower voltage or even high voltage prospects of a power transformer.
The voltage of the system is applied over the terminals of the primary winding of that transformer, after which secondary voltage appears in proper proportion over the secondary terminals of the potential transformer. Between the phase and the ground primary of the voltage transformer is connected. High voltage transformers for electric propulsion are already available from all major suppliers for current state of the art power processing units.
Special antiferro-resonance devices that use a parallel-tuned circuit are sometimes built into the VT. Although such arrangements help to suppress ferro-resonance, they tend to impair the transient response, so that the design is a matter of compromise. The spark gap limits the short-circuit current which the VT delivers and fuse protection of the secondary circuit is carefully designed with this in mind. The solution is to use a high secondary voltage and further transform the output to the normal value using a relatively inexpensive electromagnetic transformer.
Each magnetic core has primary windings (P) on two opposite sides. Voltage transformers for medium voltage circuits have dry type insulation, but high and extra high voltage systems still use oil immersed units. Voltage transformers are commonly used with switchgear so the physical design must be compact and adapted for mounting in or near to the switchgear Three-phase units are common up to 36kV but for higher voltages single-phase units are usual.
A short circuit on the secondary circuit wiring produces a current of many times the rated output and causes excessive heating. Voltage transformers for such types of service must comply with the extended range of requirements set out in Table 2. The most common voltage sources for power system measurements and protections are either wound transformers (voltage transformers) or capacitive divider devices (capacitor voltage transformers or bushing potential devices).