Voltage (current) transformer use conditions and precautions - Database & Sql Blog Articles

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Inductance

First, the conditions of use:

Unless otherwise specified, the transformer must meet the following operating conditions.
1. Ambient temperature:
The indoor environment should be between -5°C and 40°C, while outdoor models can operate between -35°C and 40°C. The average daily temperature should not exceed 30°C.
2. Altitude:
The altitude should not exceed 1,000 meters. If used in high-altitude areas, a plateau version should be selected for enhanced performance.
3. Current Transformer:
It is allowed to operate continuously at 1.2 times the rated current.
4. Voltage Transformers:
Ungrounded voltage transformers can run continuously at 1.2 times the rated voltage. Grounded ones can operate for up to 8 hours at 1.9 times the rated voltage.

Second, note:

When performing the power frequency withstand voltage test on the primary winding, it should be conducted at 80% of the specified test voltage.
Do not perform a power frequency withstand voltage test between the two primary terminals of the voltage transformer if the voltage exceeds the rated voltage factor, as this may damage the transformer.
For semi-insulated grounding voltage transformers, the inductive withstand voltage test should only be performed during insulation testing between the primary and secondary windings and ground.
When conducting a power frequency withstand voltage test between the busbar and ground or between busbars, the grounding voltage transformer must be removed from the line to prevent damage due to improper handling.
Fully insulated grounding and ungrounded voltage transformers can undergo power frequency withstand voltage tests during insulation testing, but ensure that both primary terminals are securely connected before applying high voltage.

Third, usage instructions:

1. The old standard for current transformer protection accuracy (GB1208-75) used codes "C", "D", and "B" to represent "poor", "moving", and "protection", respectively.
According to GB1208-87 and GB1208-97, the protection accuracy level is defined as the maximum allowable composite error percentage at the rated accuracy limit primary current, followed by the letter "P". Standard levels include 5P and 10P. For example, 10P15 means that the composite error is less than 10% when the primary current is 15 times the rated value.
2. The winding used for grounding protection in voltage transformers was previously called the “zero sequence voltage coil.” The correct designation is “3B” or “6B.” Here, “3” and “6” indicate the error limits, and “B” stands for “protection.”
GB1207-1997 specifies that the accuracy level for protection voltage transformers refers to the maximum allowable voltage error percentage within the range of 5% to the rated voltage factor. It is followed by the letter "P," with standard levels being "3P" and "6P."
3. Current transformers can have measurement accuracy grades such as 0.5S or 0.2S. Their secondary currents can be either 5A or 1A. If the accuracy grade changes or the secondary current is 1A, the technical parameters such as the rated dynamic and thermal stability current may need to be updated and clearly stated in the order.