For power transformers, the protection is to be provided usually against dangerous overloads and excessive temperature rise. Dangerous overloads may be due to external faults or the internal ones. External faults, however, are cleared by the relay system outside the transformer within the shortest possible time in order to avoid any danger to the transformer due to these faults. Hence [...]
The differential protection used for power transformers is based on Merz-Price circulating current principle. Such protection provides protection against internal phase-to-phase and phase-to-earth faults and is generally used for transformers of rating exceeding 2 MVA. This protection system as applied to power transformers is fundamentally the same as that for generators but with certain complicating features not encountered in the [...]
Summation devices are employed to compare the relaying quantities derived from the currents in the three phases of the primary circuit. The effectiveness of the comparison of the derived relaying quantities may be considered in terms of the effective ratio of the primary currents under comparison, such as at the two ends of a feeder. Summation devices are employed for [...]
The following points highlight the nine main types of transformers used in electronic equipments. The types are: 1. Isolation Transformers 2. Current Transformers 3. Auto Transformers 4. Pulse Transformers 5. Audio Transformers 6. Radio Frequency Transformers 7. Intermediate Transformers 8. Rectifier Transformers 9. Constant Voltage Transformers. Type # 1. Isolation Transformers: In these transformers, the primary and secondary coils have [...]
The following points highlight the two main types of power transformers. The types are: 1. Current Transformers (CTs) 2. Potential Transformers (PTs). Type # 1. Current Transformers (CTs): Current transformers are connected in ac power circuits to feed the current coils of indicating and metering instruments (ammeters, wattmeter’s, and watt-hour meters) and protective relays. Thus the CTs broaden the limits [...]
Voltage Regulation is the way in which the secondary terminal voltage varies with the load depends upon load current, the internal impedance and the load power factor. The change in secondary terminal voltage from no-load to full-load, with primary voltage and frequency held constant, is termed the inherent regulation. The figure of merit which determines the voltage characteristic of a [...]
The equivalent circuit of any device can be quite helpful in predetermination of the behaviour of the device under various conditions of operation and it can be drawn if the equations describing its behaviour, are known. If any electrical device is to be analysed and investigated further for suitable modifications, its appropriate equivalent circuit is necessary. The equivalent circuit for [...]
In this article we will discuss about the formula of emf equation. When an alternating (sinusoidal) voltage is applied to the primary winding of a transformer, an alternating (sinusoidal) flux, as shown is Fig. 10.2., is set up in the iron core which links both the windings (primary and secondary windings). Let ɸmax = Maximum value of flux in webers [...]
Depending upon the type of construction used, the transformers are classified into two categories viz.: (i) Core type, and (ii) Shell type. Depending upon the type of service, in the field of power system, they are classified as: (i) Power transformers, and (ii) Distribution transformers. 1. Core Type and Shell Type Transformers: In core type construction, as shown in Fig. [...]
The following article will guide you about how to determine transformer efficiency. Meaning of Transformer Efficiency: The rated capacity of a transformer is defined as the product of rated voltage and full-load (rated) current on the output side. The power output depends upon the power factor of the load. The efficiency (η) of a transformer, like that of any other [...]