Voltage Transformer

The current transfortners and voltage transformers, when tised, must conform to lEC 60044 and lEC 60186, as noted in the list of standards. Instrument transformers with the following accuracies must be used ... 

X6/1987 Measuring voltage transformers Protective voltage transformers Capacitor voltage transformers. "1156-2/1992. 1156-3/1992 3156-4/1992 BS 7729/1995 BS 7625/1993 ... 

Application Guide for voltage transformers Specification for voltage transformers General requirements 4201/1991 4146/1991 BS 7625/1993 BS 7629/1995... 

General specifications and design considerations for voltage transformers (VTs) 15/457... 

Precautions to be observed while installing a voltage transformer 15/469... 

This is not material in voltage transformers, as neither the voltage measuring instruments nor the protective relays will carry any inrush current during a switching operation or a fault. No short-time rating is thus assigned to such transformers. 

Measuring voltage transformers Standard accuracy class may be one of 0.1, 0.2, 0.5, I or 3. The recommended class of accuracy will depend upon the type of metering and generally as noted in Table 15.3. 

Loss component of current supplying the hysteresis and eddy current losses to the voltage transformer core (it is the active component)... 

Figure 15.1 Equivalent circuit diagram for a voltage transformer...

Figure 15.3(a) Typical indoor epoxy resin cast instrument voltage transformers up to 11 kV (Courtesy Kappa Electricals)... 

The size and therefore the cost of a conventionally wound voltage transformer will be almost proportional to the system voltage for which it is wound. As a cost consideration, therefore, a more economical alternative is found in a Capacitor Voltage Transformer (CVT) (Figure 15.6(a)). 

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