What is back charging of power transformer?

What is back charging of power transformer?

Back charging is applying rated secondary voltage to the secondary terminals. Your secondary switchgear should be adequate to handle the fault current. It should be able to handle the inrush. There may be an objectionable voltage dip on the 11 kV circuit due to the inrush current.

What happens if generators are not synchronized?

Poor synchronizing can: Damage the generator and the prime mover because of mechanical stresses caused by rapid acceleration or deceleration, bringing the rotating masses into synchronism (exactly matched speed and rotor angle) with the power system.

What are the requirements for synchronizing generators?

There are five conditions that must be met before the synchronization process takes place. The source (generator or sub-network) must have equal line voltage, frequency, phase sequence, phase angle, and waveform to that of the system to which it is being synchronized.

How do you synchronize a transformer?

The standard method of connecting transformers in parallel is to have the same turn ratios, percent impedances, and kVA ratings. Connecting transformers in parallel with the same parameters results in equal load sharing and no circulating currents in the transformer windings.

Can I reverse a transformer?

Yes, you can use the transformer in reverse, but note that the ratio is usually adjusted up by 5-10% to allow for the voltage loss under rated load due to winding resistance. When you use it in reverse, that will result in a lower output voltage than expected.

What is the purpose of soaking a transformer?

A soak to thermal stability also provides a good opportunity to verify that all of the radiators are at approximately the same temperature before putting full load on the transformer.

Why do we need to synchronize two generators?

The need for synchronization arises when two or more alternators work together to supply the power to the load. Since electrical loads do not remain constant, the two or more generators supplying the power need to be interconnected and operate in parallel to handle larger loads.

How do you sync two or more generators?

For two generators to be synchronized; the waveform of their output must match with one another. This can be achieved by using a synchroscope or dark and bright lamp methods. To ensure further safety; it is required to keep the incoming generator at sightly higher frequency.

Why is synchronization needed?

The need for synchronization originates when processes need to execute concurrently. The main purpose of synchronization is the sharing of resources without interference using mutual exclusion. The other purpose is the coordination of the process interactions in an operating system.

What is the effect of wrong synchronization?

An improper synchronization can affect the healthy power system and results in electrical and mechanical transients that can damage the prime mover, generator, transformers and other power system components.

Can two transformers be connected in parallel?

Introduction. For supplying a load in excess of the rating of an existing transformer, two or more transformers may be connected in parallel with the existing transformer. The transformers are connected in parallel when load on one of the transformers is more than its capacity.

What happens when two transformers are connected in series?

Series Connected Secondary Transformer As the two windings are connected in series, the same amount of current flows through each winding, then the secondary current is the same at 2.5 Amps.

Why does a generator need to be synchronized with the power system?

Every time before reconnecting the generator to the system, it must be synchronized with parameters of the power system network. An improper synchronization can affect the healthy power system and results in electrical and mechanical transients that can damage the prime mover, generator, transformers and other power system components.

What is the process of synchronization of alternators called?

Synchronization matches various parameters of one alternator (or generator) to another alternator or to the bus bar. The process of synchronization is also called as paralleling of alternators.

Is the phase sequence of the generator the same as the grid?

The phase sequence (or phase rotation) of the three phases of the generator must be the same as the phase sequence of the three phases of the electrical system (Grid). The only time that the phase sequence could be wrong is at initial installation or after maintenance. There are two possible problem sources.

Why is a generator slower than the grid?

In Figure 2 above the generator is slower than the grid. The synchroscope would be rotating rapidly counter clockwise. If the generator breaker were to be accidentally closed, the generator would be out of step with the external electrical system. It would behave like motor and the grid would try to bring it up to speed.