Current transformers work in a high-voltage electrical environment. While they are critical to the safety of the equipment and people working down the electrical lines, certain precautionary measures must be taken for the protection of the current transformer and the personnel working on it.
Consider these 4 precautionary measures when using a current transformer
What: Ensure that the polarity connections are correct
Why: Current transformers generally feature markings denoting negative polarity. If the polarity is incorrect, the connected devices start malfunctioning. The energy meter will show negative readings and the relay will read the negative current. This will lead the relay to activate the trip circuit. In many cases, even when there are multiple CTs in parallel on the same line, all of them can cause a short circuit.
What: Allot a protective point to the secondary circuit
Why: Proper current transformer grounding is vital for the secure and smooth operation of protective relays. Current transformer secondary grounding is done at multiple points does not exactly cause any issues under normal conditions. However, in case of a fault, the potential at the different grounding points of the current transformer will rise at different rates. This leads to a high current flow through the CT circuit, and this current is not representative of the primary current. This makes the relay believe that there is a fault in its protective zone, and trip.
What’s more, the grounding for all CTs should be done at a single point. Learn the basics of CT grounding on our blog here
What: Do not use a protection-type CT for measuring purpose and vise-versa
Why: The protection type current transformers are designed to operate under high levels of fault current. If they are connected to meters under normal operation, it will affect the measuring accuracy of the meters. Additionally, high current will be passed on to the meters, causing severe damage to them.
Find out what happens if protection and measuring CTs are interchanged
What: Do not leave the secondary circuit open during operations
Why: If the CT secondary is left open, it may endanger the safety of the CT device as well as personnel working to install or maintain a CT.
An open CT secondary can result in the following consequences
- HIgh voltage is created on the secondary side endangering the safety of personnel
- Accuracy in measurement is affected
- Winding burns out due to overheating
Explore the phenomenon deeper in our blog here
Conclusion
Being electrical devices, the safety and efficiency of current transformers is a key consideration. Alongside correct installation practices, the build quality of the current transformer is also an important point. If the current transformer falls due to mishandling or other factors, it is rendered inoperable, and replacement of the damaged unit entails considerable costs and downtime.
Newtek Electricals has been working for over a decade to resolve these serious concerns of users with its innovative current transformer designs. Newtek is the first current transformer manufacturer in India to introduce a nylon casing current transformer. These transformers are resistant t damage from a fall or from fire and offer reliable performance over decades.
To know more, write to us at sales@newtekelectricals.com