2.7 Voltage Sag: Voltage Regulation Devices III

A static VAR compensator (SVC) is a set of electrical devices for providing fast-acting reactive power on high-voltage electricity transmission networks.
SVCs are part of the FACTS device family, regulating voltage, power factor, harmonics and stabilizing the system.

7. Line drop Compensator:

The line-drop compensator comprises an 'artificial line' circuit consisting of adjustable resistances and reactance connected into the voltage relay operating-coil circuit.

UPS stands for Un-interrupted Power Supply, also known as Un-interrupted Power Source.
It is a power system provide continuous power supply or a battery backup which maintain a continuous supply to connect equipment by supplying power from a separate source when utility power is not available.

The static UPS is called “static” because, throughout its power path, it has no moving parts.
The rectifier inside of the static UPS converts the incoming utility AC current to DC, and the inverter converts DC back to clean sine-wave AC to supply the load.
The DC current interfaces with the “energy storage” medium – most commonly batteries, in which case it charges the batteries and receives power from the batteries when the utility power supply is distorted or fails.

The rotary UPS is called “rotary” because rotating components (such as a motor-generator) within the UPS are used to transfer power to the load.
Rotary technology has been utilized for many years and came into use at a time when loads would commonly exhibit a low power factor (which resulted in increased losses in the power distribution system and thus, an increased energy cost) and high harmonics (which prematurely shortened the life of transformers and capacitors).
For Example, Users would experience the dimming of lights, brought on by voltage dips and sags, when large motors turned on.
These load characteristics, in turn, would destabilize the electronics of connected loads within the electrical network. Thus, the introduction of the rotary UPS to address this issue.

In an On-line UPS, the load is always fed through the UPS.
The incoming ac power is rectified into DC power which charges a battery bank.
This dc power is then inverted back into ac power to fed the load.
If the incoming ac power fails, the inverter is fed from the battery of UPS and continue supply load.
The On-line UPS in addition provides protection against complete failure of the utility power supply, protection against all common problems and hence, it is also known as Power Conditioner and a Line Conditioner.

In it, the normal line power is used to power the equipment until a disturbance is detected and a switch transfer the load to the battery backup inverter.
In this, the primary power sources i.e., line powers from the utility and the secondary power source is a battery.
It is called standby UPS because the battery and inverter are normally not supplying power to the equipment.
The battery charger uses line power to charge the battery and the battery-inverter are waiting on standby until they are needed.
When ac power goes off, the transfer switch change to the secondary power source.
A standby power supply does not typically provide any transient protection or voltage regulation as does an on-line UPS.

Hybrid UPS:

It is similar in design to the Standby UPS.
The hybrid utilizes a voltage regulator on the UPS output to provide regulation to the load and momentary ride-through when the transfer from normal to UPS supply is made.

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