Potential transformer symbol

A current transformer ( CT) is a type of Current transformers, along with voltage or potential transformers, are Current transformers are the current-sensing units of the power system and are used at generating stations, electrical substations, and in industrial and commercial electric power distribution. Function [ ] A current transformer has a primary winding, a core, and a secondary winding, although some transformers, use an air core. While the physical principles are the same, the details of a "current" transformer compared with a "voltage" transformer will differ owing to different requirements of the application. A current transformer is designed to maintain an accurate ratio between the currents in its primary and secondary circuits over a defined range. The Current transformers typically consist of a CTs are specified by their current ratio from primary to secondary. The rated secondary current is normally standardized at 1 or 5amperes. For example, a 4000:5 CT secondary winding will supply an output current of 5amperes when the primary winding current is 4000 amperes. This ratio can also be used to find the impedance or voltage on one side of the transformer, given the appropriate value at the other side. For the 4000:5 CT, the secondary impedance can be found as Z S = NZ P = 800Z P, and the secondary voltage can be found as V S = NV P = 800V P. In some cases, the secondary impedance is referred to the primary side, and is found as Z S′ = N 2Z P. Referring the im...

Contents • 1 Overview • 1.1 Scaling • 2 Equipment • 2.1 Current Transformers • 3 Potential Transformer Circuits • 3.1 Three-Wire Delta Service • 3.2 Four-Wire Wye Service • 3.3 Three-Wire Wye Service (No Neutral) • 4 Configuring the PT Ratio • 4.1 WattNode for LonWorks – Option PT • 4.2 WattNode Modbus • 4.3 WattNode Pulse • 5 Notes • 5.1 Energy Rollover • 5.2 PT Burden • 6 See Also Overview WattNode ® meters are available in seven voltage ranges up to 600 Vac line-to-neutral, as well as wide-range models that operate from 100 to 600 Vac. For service voltage above 600 Vac, potential or voltage transformers (PTs or VTs) are used to step down the voltage to a lower range that will work with a WattNode meter. PTs are used for medium-voltage services above 600 Vac, but also sometimes for 575-600 Vac three-phase three-wire delta circuits. WattNode ® for BACnet ®, LonWorks, and Modbus meters support PT ratios and can scale measurements internally. Older models and pulse models will need to have the data scaled externally by the data collection system. If you are using a WattNode ® for LonWorks ® meter, we offer UCPTptRatio which configures the ratio of the external PT, allowing the meter to automatically scale the voltage, power, and energy readings. Scaling Adding potential transformers has the effect of reducing the measured line voltage by the PT ratio (let’s say 35:1 for this example). So a voltage of 4200 Vac becomes 120 Vac. Since the meter sees 120 Vac, many of the measur...

Voltage transformers (VT), also called potential transformers (PT), are a parallel-connected type of Ratio [ ] The PT is typically described by its voltage ratio from primary to secondary. A 600:120 PT will provide an output voltage of 120volts when 600volts are impressed across its primary winding. Standard secondary voltage ratings are 120volts and 70volts, compatible with standard measuring instruments. Burden and accuracy [ ] Burden and accuracy are usually stated as a combined parameter due to being dependent on each other. Metering style PTs are designed with smaller cores and VA capacities than power transformers. This causes metering PTs to saturate at lower secondary voltage outputs saving sensitive connected metering devices from damaging large voltage spikes found in grid disturbances. A small PT (see nameplate in photo) with a rating of 0.3W, 0.6X would indicate with up to W load (12.5 watts Markings [ ] Some transformer winding primary (usually high-voltage) connecting wires are of many types. They may be labeled as H 1, H 2 (sometimes H 0 if it is internally designed to be grounded) and X 1, X 2 and sometimes an X 3 tap may be present. Sometimes a second isolated winding (Y 1, Y 2, Y 3) (and third (Z 1, Z 2, Z 3) may also be available on the same voltage transformer. The primary may be connected phase to ground or phase to phase. The secondary is usually grounded on one terminal to avoid capacitive induction from damaging low-voltage equipment and for human s...

Learn To Interpret Single Line Diagram - SLD (on photo: An example of 66/6.6kV power substation single line diagram) We use universally accepted electrical symbols to represent the different electrical components and their relationship within a circuit or system. To interpret SLDs you first need to be familiar with the electrical symbols. This chart shows the most frequently used symbols. Individual electrical symbols Symbol Identification Explanation Transformer Represents a variety of transformers from liquid filled to dry types. Additional information is normally printed next to symbol indicating winding connections, primary /secondary voltages and KVA or MVA ratings. Removable or drawout circuit breaker Normally represents a MV drawout circuit breaker 5kV and above. Future removable or drawout circuit breaker position Represents a structure equipped to accept circuit breaker in the future, commonly known as provisions. Non-drawout circuit breaker Represents a fixed mounted low voltage circuit breaker. Removable or drawout circuit breaker Represents a drawout low voltage circuit breaker. Disconnect switch Represents a switch in low or medium/high voltage applications (open position shown) Fuse Represents low voltage and power fuses. Bus duct Represents low and medium/high voltage bus duct. Current transformer Represents current transformers mounted in assembled equipment. A ratio of 4000A to 5A shown. Potential or voltage transformer Represents potential transformers us...

This is the most common type of transformer, widely used in electric power transmission and appliances to convert Small appliance and electronic transformers may use a split bobbin, giving a high level of insulation between the windings. The rectangular cores are made up of stampings, often in E-I shape pairs, but other shapes are sometimes used. Shields between primary and secondary may be fitted to reduce EMI (electromagnetic interference), or a screen winding is occasionally used. Small appliance and electronics transformers may have a Toroidal [ ] Donut-shaped Toroidal transformers have a lower external magnetic field compared to rectangular transformers, and can be smaller for a given power rating. However, they cost more to make, as winding requires more complex and slower equipment. They can be mounted by a bolt through the center, using washers and rubber pads or by potting in resin. Care must be taken that the bolt does not form part of a short-circuit turn. Autotransformer [ ] A leakage transformer, also called a stray-field transformer, has a significantly higher The output and input currents are kept low enough to preclude thermal overload under any load conditions — even if the secondary is shorted. Uses [ ] Leakage transformers are used for Other applications are short-circuit-proof Resonant transformer [ ] Further information: A Resonant transformers are also used in sc and the resonant capacitor (or stray capacitance) of the secondary side is C r, The reson...