transformer
11kv 3 Phase 200kva Distribution Transformer
Distribution transformers normally have ratings less than 200 kVA,although some national standards can allow for units up to 5000 kVA to be described as distribution transformers. Since distributio...
DESCRIPTION
Distribution transformers normally have ratings less than 200 kVA,although some national standards can allow for units up to 5000 kVA to be described as distribution transformers. Since distribution transformers are energized for 24 hours a day (even when they don’t carry any load), reducing iron losses has an important role in their design. As they usually don’t operate at full load, they are designed to have maximum efficiency at lower loads. To have a better efficiency, voltage regulation in these transformers should be kept to a minimum. Hence they are designed to have small leakage reactance.
Distribution Type Transformer Technical Data
| Rated Capacity: | 200 kVA; |
| Mode: | S13-M.R-200/11 or depends; |
| Primary Voltage: | 11kV; |
| Secondary Voltage: | adhere to clients; |
| No Loading Loss: | 240 ±10% W; |
| Loading Loss: | 2600 ±10% W; |
| Impedance: | 4.0% ± 10%; |
| Insulation Material: | Mineral Oil or epoxy resin; |
| Power Frequency withstand Voltage: | 35kV; |
| Lighting Impulse withstand Voltage: | 75kV. |
3 Phase 200kva Distribution Transformer Maintenance
1.Capacity:
During normal operation, the electrical load on the 11kv 3 phase 200kva distribution transformer should be maintained at approximately 75-90% of the transformer’s rated capacity.
2.Temperature:
Temperature gauges installed on the 11kv 3 phase 200kva distribution transformer should be recorded during routine inspections. For unattended transformers, voltage, current, and upper oil temperature should be recorded during each scheduled inspection. Additionally, for distribution transformers, the load on certain phases should be measured during peak load periods. If an imbalance is detected, redistribution should be considered. The measurement period should comply with on-site regulations.
3.Insulation Monitoring:
Before commissioning or after major maintenance, 11kv 3 phase 200kva distribution transformers should have their coil insulation resistance measured (usually after drying) and the values obtained, along with the measurement oil temperature, should be recorded in the transformer’s history card. The insulation resistance of coil windings should be measured using a megohmmeter with a range of 1000 to 2500 volts. Specific allowable insulation resistance values are not defined.
The comparison between the insulation resistance values measured during transformer operation and those obtained before commissioning or after drying serves as a primary indicator of the transformer’s insulation condition. Insulation resistance measurements should be conducted at the same temperature, using the same megohmmeter voltage, as much as possible.
4.Current Range:
The maximum allowable imbalance current at low voltage terminals of the 11kv 3 phase 200kva distribution transformer should not exceed 25% of the rated value. The permissible range for source voltage variation is within±5% of the rated voltage.
5.Overloading:
In exceptional cases, 11kv 3 phase 200kva distribution transformers can operate at an overload for a short duration, but during winter, the overload should not exceed 30% of the rated load, and during summer, it should not exceed 15% of the rated load.
