Current Transformer

Before discussing the Rogowski Coil CT (Current Transformer), it is essential to understand the basic theory behind it. When current flows through a conductor, it creates a magnetic field around that conductor. If we place a ring-shaped magnetic core around the conductor, the magnetic flux lines concentrate inside the core. When we wrap a copper … Read more

Wound Type CT The Wound type CT uses a magnetic core. The core of the CT consists of laminations of cold-rolled, grain-oriented silicon steel. Some manufacturers also use nano-crystalline core material for this purpose. This creates a closed magnetic path. We wrap insulating paper around this closed magnetic path (core). Over the paper insulation, we … Read more

A high-voltage power system deals with a huge quantity of currents. Unfortunately, the huge size of meters or protection relays is not available in the market. For cost and size optimization, the meters and relays are normally designed with a 1 A or 5 A rating. Therefore, there must be some means by which we … Read more

Nowadays, SF6 gas-filled current transformers become popular modern type of CT used in high-voltage substations. It uses SF6 gas as its internal insulating medium instead of conventional insulating oil. We normally install SF6 CTs in voltage levels above 132 kV. A typical SF6 CT is a single-unit, live-tank type instrument transformer. Because it contains pressurized … Read more

Current Transformers (CTs) play a crucial role in power systems. They perform both metering and protection functions. However, the same CT can not perform both metering and protection functions. This is because each of the protection and metering applications has different accuracy, burden-handling, and dynamic performance requirements. Hence, CTs are designed as either Metering CTs … Read more

Current transformers (CTs) play a critical role in protection and metering. The proper operation of protection relays depends on CT accuracy to detect faults. Additionally, the accuracy of CT is more important for metering purposes. However, when a CT experiences core saturation, its secondary output no longer represents the true replica of the primary current. … Read more

Current Transformers are essential for protection and measurement. To work correctly, they must reproduce primary current in a fixed ratio on the secondary side. However, CTs are not ideal. They suffer from three major types of errors. Ratio Error (Magnitude Error) in CTs The CT can not produce the exact scaled-down current. The actual secondary … Read more

A current transformer (CT) reduces high currents to small, usable values. We utilize CTs for metering and protection purposes. Proper CT selection ensures accuracy, safety, and reliable protection. Identify the Purpose of CT Metering CT A metering CT measures current for billing and monitoring. Therefore, it must work accurately within the tolerable upper limit of … Read more

We also refer to the Core Balance Current Transformer or Core Balance CT (CBCT) as Working Principle of Core Balance CT (CBCT) A Core Balance Current Transformer (CBCT) is a special type of current transformer. Specifically, it works on the principle of imbalance detection. It monitors the imbalance current of a three-phase cable system. When … Read more

In this article, we are going to discuss the dead tank CT or dead tank current transformer, commonly referred to as a dead tank CT. Dead tank current transformers are not popular for very high-voltage systems like 220 kV and above. Utilities often use dead tank CTs in 33 kV systems. They prefer this design … Read more