Voltage transformers. (A) The primary winding of VTs must be connected to the circuits being measured.
Voltage transformers. 15- Routine tests ▪ Verification of terminal markings. ▪ Power- frequency voltage withstand test on the primary terminals. ▪ Partial discharge measurements. ▪ Power-frequency voltage withstand test on secondary terminals. ▪ Power – frequency voltage withstand test between sections. ▪ Determinations of errors (accuracy test for phase angle and ratio errors). ▪ Measurement of primary and secondary winding resistance. ▪ Pressure test for the enclosure. ▪ Enclosure tightness test at ambient temperature. 16- Type tests
Voltage transformers. For the 220 kV levels, capacitive transformers shall be provided, according to the application. It must be taken into account that the transformers shall not produce ferro resonance effects associated with the overhead line capacities. Voltage transformers shall have the following main characteristics: Description 220 kV Type of insulation Outside Secondary voltage 110/√3 V Characteristic of measurement cores a) Accuracy class b) Power 0,2 % 15 VA Characteristics of protection cores a) Accuracy class b) Power 3P 15VA
Voltage transformers. Voltage transformers shall be suitable for the operation of protective gear, voltage regulating equipment, instruments and/or metering and shall be of the wound type. Voltage transformers shall be in accordance with IEC 60044 with a rated voltage factor of l.2. Voltage transformers shall be capable of carrying continuously, without injurious heating, 50% burden above their rated burden. The rated primary voltage of voltage transformers shall be the appropriate nominal system voltage. Unless specified, voltage transformer primary windings shall be connected to the circuit side of the current transformers remote from the busbars so as to be included in the protected zone of the associated feeder. The primary of a single phase voltage transformer shall be connected across Red and Yellow or A and B phases, unless otherwise approved. Red and Yellow phases shall be used in a synchronising scheme, unless otherwise approved. Voltage transformers shall be capable of being connected and disconnected from the equipment whilst in service. Facilities for padlocking in the service position shall be provided. Where isolation is carried out by withdrawal, a set of shutters, capable of being padlocked, shall be provided to cover the stationary isolating contacts. The shutters shall operate automatically by positive drive actuated by movement of the voltage transformer assembly. The primary windings shall preferably be connected via renewable fuses with current limiting features which shall be readily accessible with the circuit alive and the secondary windings through fuses and links, labelled to indicate their function and phase colour, to the appropriate circuits. For single phase voltage transformers, both ends of each secondary winding shall be brought out to insulated links. For three-phase voltage transformers, each phase end shall be brought out to fuses, and the neutral of the secondary winding shall be brought out to insulated links. The fuses and links shall then be brought out to insulated terminals located in a terminal box. The primary and secondary fuses shall be capable of being removed and replaced when the circuit-breaker is closed in the service position. Isolation of the primary fuses for this purpose shall be carried out, preferably by withdrawing the entire voltage transformer assembly. Additionally, it shall be possible to remove secondary fuses whilst the voltage transformer is padlocked in the service location. For single phase units, separate earth...
Voltage transformers. All voltage transformers shall be checked for polarity, phasing and secondary output. All electromagnetic type voltage transformers shall have insulation tests carried out on them at 500 Volts to earth and between windings.
Voltage transformers. ITEM 11KV SWITCHGEAR VT 11KV GENERATOR NGT 220KV SWITCHYARD VT -----------------------------------------------------------------------------------------------------
Voltage transformers. Voltage transformers shall be of the capacitor type and shall comply with IEC 60044-2 and the requirements of this specification. Capacitor type transformer shall be suitable for use as line couplers for power line carrier communication systems. Ratings: Rated Primary Voltage: 220 kV/[X]3 Rated Secondary Voltage: 110 V/[X]3 The rated Burden and Class shall be suitable for the connected Protection Relays and other devices.
Voltage transformers. Where required a VT to IEC Standard 186 and with a minimum standard of accuracy to Class 1 shall be provided for the metering of a circuit. The voltage transformer may be used for other purposes provided the overall accuracy requirements in Section 4.2.1 are met and evidence of the value of the additional burden is available for inspection by Scottish Settlements. The additional burden shall not be modified without prior notification to Scottish Settlements, and evidence of the value of the modified additional burden shall be available for inspection by Scottish Settlements. A VT test certificate(s) showing errors at the overall working burden(s) or at burdens which enable the working burden errors to be calculated shall be available for inspection by Scottish Settlements. The total burden on each secondary winding of a VT shall not exceed the rated burden of such secondary winding. The VT supplies shall be fused as close as practicable to the VT, with a set of isolating links, suitably identified provided locally to the Metering Equipment.
Voltage transformers a. The insulation post should be Silicon rubber and the VT body should be resin or equivalent material (Porcelain and oil type not accepted) and it must have environmental type test b. V.T’S ratio (33/√3: 0.110/√3) KV out door pole mounted with creepage distance not less than 1188 mm.
