The secondary winding maintains the high voltage instrument transformers force to sustain this flux and circulates a current through the burden, which decays more or less exponentially.
When the supply to a voltage transformer is interrupted, the core flux does not immediately collapse. If a voltage is suddenly applied, an inrush transient occurs, as with power transformers. The residual voltage of a system is measured by connecting the secondary windings of a VT in ‘broken delta’ as shown in Figure 4.
The construction of a voltage transformer differs from that of a power transformer in that different emphasis is placed on cooling, insulation and mechanical design. Even where primary fuses can be fitted, these usually do not clear a secondary side short circuit because of the low value of primary current and the minimum practicable fuse rating. The secondary of a Voltage Transformer should always be protected by fuses or a miniature circuit breaker (MCB).
Voltage Transformers can be protected by High Rupturing Capacity (H.R.C.) fuses on the primary side for voltages up to 66kV. The phase error is the phase difference between the reversed secondary and the primary voltage vectors. The secondary output voltage Vs is required to be an accurate scaled replica of the input voltage Vp over a specified range of output.
Voltage transformer can be represented by the equivalent circuit of Figure 1, where all quantities are referred to the secondary side. Even protection-type voltage transformers can provide revenue-metering performance if the burden is carefully controlled. 12-24-36 kV WITH FUSE BLOCK TYPE SINGLE POLE VOLTAGE TRANSFORMERS.
Site Transformers Voltage Transformers Wide range of site transformers at to ensure safety on site. OTCF Coupling Capacitor Voltage Transformers up to 765 kV In high and extra high voltage transmission systems, capacitor voltage transformers (CVTs) are used to provide potential outputs to metering instruments and protective relays. Thousands voltage transformers are in service worldwide, in all types of climates and under the most severe conditions.
OTEF Oil-Insulated Voltage Transformers up to 550 kV GE manufactures a complete range of high voltage oil-filled voltage transformers (VTs). They provide accurate and reliable current and voltage measurements for secondary equipment such as meters, protections relays, bay computers and other devices. Earthed voltage transformers can be equipped with an additional winding for earth-fault monitoring.
Whether you are looking for current transformers, current sensors or AC/DC-sensitive safety devices, we offer solutions which meet the expectations towards highest quality and tightest tolerances. We offer various materials, stamped parts and inductive components such as differential current sensors or current transformers to support you in your solution. Our current transformers offer many technical advantages, such as a high level of linearity, low temperature dependence and a compact design.
We supply leading smart meter manufacturers in the IEC and ANSI markets with VAC current transformers and support our customers very successfully for more than 20 years. Current Transformers for 50 Hz/60 Hz energy meters require core materials with highest permeability and linearity. Internally, the current flow in the conductor can be measured either as a current—some older clamp accessories plug into the current jacks of a digital multimeter—or can be converted to a voltage.