What is the difference between Oltc and Octc?
On-load tap changer (OLTC), also known as On-circuit tap changer (OCTC), is a tap changer in applications where a supply interruption during a tap change is unacceptable, the transformer is often fitted with a more expensive and complex on load tap changing mechanism.
What is function of Oltc in transformer?
Power transformers equipped with on-load tap- changers (OLTCs) have been the main components of electrical networks and industrial applications for nearly 90 years. OLTCs enable voltage regulation and/or phase shifting by varying the transformer ratio under load without interruption.
How many taps are in Oltc?
On-Load Tap Changing Transformer (OLTC) using a Resistor
It consists of resistors r1 and r2 and 4 taps t1, t2, t3, t4.
What is the difference between on load tap changer and off load tap changer?
Unlike in on-load tap changing where the arc quenching is limited by oil when the transformer is on-load, the tapping with an off-load tap changer is only carried out when the transformer is in OFF-Switch condition.
What are the disadvantages of tap changing transformer?
However, its major disadvantage is that although two thyristor are ON over short periods during the tap-changing process, it is permanently connected to the circuit of the deviation switches and it probably gets burnt. This may therefore reduce the reliability of the system.
How do you calculate tap voltage?
can be calculated as: Turns ratio for each tap is calculated by dividing rated tap voltage from name plate with rated secondary voltage. For example, to calculate turns ratio for +2.5% tap we divide 14,145V/480V to get 29.47.
Where is Oltc connected?
On Load Tap Changer or OLTC
The tapping arrangement, is placed in separate divertor tank attached to electrical power transformer main tank. Inside this tank, the tap selectors are generally arranged in a circular form.
What is PRV in transformer?
Pressure Relief Valve (PRV) is a safety device for Transformers, OLTC and other similar equipments. PRV is used to prevent heavy damages to the tank in case of sudden rise of internal pressure beyond pre determined safe limit. MOUNTING.
What is Oti in transformer?
They are commonly referred to in the industry as Oil Temperature Indicators (OTI) and Winding Temperature Indicators (WTI). Electrical utilities often utilize oil and winding temperature indicators to provide alarm and control signals that are used to activate cooling control systems on a transformer.
What are the types of transformer tap changer?
There are two types of transformer tap changers: an on-load tap changer (OLTC) and a deenergised tap changer (DETC).
Why kVA rating is used in transformer?
As, the copper loss or I2R loss depends on the current and the iron or core loss depends upon the voltage of the transformer. Thus, the total losses in a transformer depend upon volt-ampere (VA) only and not on the power factor of the load. That is why the transformer rating is given in kVA and not in kW.
Why tap changer is connected on the HV side?
Why tap changer is placed on high voltage side? The tap changer is placed on high voltage side because: 1. The HV winding generally wound over LV winding hence it is easier to access the HV winding turns instead of LV winding.
What is a tap ratio?
Using a tap changes the voltage ratio of a transformer so that its secondary voltage stays at nominal. On large power transformers, taps on the primary are used to offset any higher or lower input voltages. These tap connections are usually set at the factory for nominal line voltage.
What is tap ratio of transformer?
Multi-Tap Transformers
| Tap percentage | Equation | New ratio |
|---|---|---|
| 95% | 10 x 0.95 = | 9.5:1 |
| 97.5% | 10 x 0.975 = | 9.75:1 |
| 100% | 10 x 1 = | 10:1 |
| 102.5% | 10 x 1.025 = | 10.25:1 |
What is OSR in transformer?
Oil Surge Relay-OSR is one of the auxiliary equipment of an oil-immersed type transformer. It is mainly used to limit the damage to the on-load tap changer in case of failure. OSR is placed in between OLTC(On Load Tap Changer) tank and OLTC conservator. Oil Surge Relay.
Why CT S2 is earthed?
To prevent the secondary circuits from attaining dangerously high potential to ground, these circuits have to be grounded. Connect either the S1 terminal or the S2 terminal to ground.
How do I convert kVA to kW?
kVA = kw / PF
PF = Power factor.
What is difference between KV and kVA?
KV = kilo volt, It always denotes a voltage value as electric voltage, EMF. Again KVA = kilo volt ampere, It denotes the value of power. As per the formula Power = current * voltage or P=VI .
What is the tap rule?
tap rule states that a cable rated for at least 10% of the rating of the upstream protective device must be used. In this example, we see that multiple taps are used coming from a single circuit breaker as long as all of the taps comply with the NEC requirements. The 10 ft.
How is tap ratio calculated?
Turns ratio for each tap is calculated by dividing rated tap voltage from name plate with rated secondary voltage. For example, to calculate turns ratio for +2.5% tap we divide 14,145V/480V to get 29.47.
Why the rating of transformer is in kVA?
The copper and iron are the two types of losses that occur in the transformer. The copper loss depends on the current (ampere) flows through the windings of the transformer while the iron loss depends on the voltage (volts). i.e., the rating of the transformer is in kVA. Was this answer helpful?
What is BDV test?
BDV test means the Breakdown Voltage Test. This test is performed for verifying the dielectric strength of the oil of the transformer. Dielectric Strength is the maximum capacity to resist the voltage of insulating oil. This test demonstrates the dielectric Strength of Transformer Oil.
Where Buchholz relay is used?
Buchholz relays have been applied on oil-filled power and distribution transformers at least since the 1940s. The relay is connected to the oil piping between the overhead conservator tank and the main oil tank of a transformer.
Why fuse is not used in CT?
Primary is the conductor which carries the large load current. If secondary of the current transformer is OPEN, like in case of a blown fuse, it can develop a very high voltage which can in the least burst the insulation. The open circuit voltage of the secondary of a current trnsformer can develop into lethal voltage.
What is P1 and P2 in CT?
P1 indicates the side on which the current source is located, whilst P2 indicates the load side.