Summation Measuring Current Transformers for Power Systems

How to select the right Current Transformer?

Current Transformers perform two critical roles in the power supply eco-system. They are used as current measurement devices and as protection relays. However, there are different types of Current Transformers and several factors govern the appropriate choice of the Current Transformer.

The objective of this study is to understand the key considerations before choosing the right Current Transformer for a particular application.

If you are looking to read about the basic function of Current Transformers, compliance standards and applications, read our earlier blog here.

SUMMATION CURRENT TRANSFORMERS

These CTs are used to sum-up the currents in a number of circuits at a time through the measuring CTs provided in each such circuit. They are used for converting the three-phase quantities into a single-phase quantity. Summation transformers are used during unbalanced or faulty conditions in the system, in order to ensure the relays operate normally.

The circuits may represent different feeders connected on the same bus of a power system or of two or more different power systems. However, for summation of currents on different power systems, all circuits must be operating on the same frequency and must relate to the same phase. The power factor may be different.

Each phase of the circuits are provided with an appropriate main CT, the secondary of which is connected to the primary of the summation CT. The summation is possible of many circuits through one summation CT alone per phase.

The summated current is the sum of the CT secondary currents of all the different circuits. The instrument transformer rating connected on the secondary of the summation CT should be commensurate with the summated current.

KSUM Series – Summation Measuring Current Transformers from KSI

KSU Series are range of Summation current transformers. Summation CTs are used to sum secondary currents of several main CTs and supply to a single meter or relay.

Features:

• Designed as per IS-6949 or Customer specific requirement
• Approved and widely used by various State Power Supply companies
• Requires little or no maintenance
• Tested and certified at CPRI Bangalore, India (NABL)
• Secondary Current 5A or 1A
• Primary Current up to 5000A
• Secondary Burden 1VA to 30VA
• Dual Ratios can be offered
• High accuracy on request
• Mounting arrangement on request
• Construction Styles Offered :
  • Varnished Fibre Glass or PVC Tape Insulated
  • Resin cast
  • ABS or Glass Filled Nylon Moulded

Learn more: KSUM Series – Summation Measuring Current Transformers from KSI

KSUP Series – Summation Protective Current Transformers from KSI

KSU Series are range of Summation current transformers. Summation CTs are used to sum secondary currents of several main CTs and supply to a single meter or relay.

Features:

• Designed as per IS-6949 or Customer specific requirement
• Approved and widely used by various State Power Supply companies
• Requires little or no maintenance
• Tested and certified at CPRI Bangalore, India (NABL)
• Secondary Current 5A or 1A
• Primary Current up to 5000A
• Secondary Burden 1VA to 30VA
• Dual Ratios can be offered
• High accuracy on request
• Mounting arrangement on request
• Construction Styles Offered :
  • Varnished Fibre Glass or PVC Tape Insulated
  • Resin cast
  • ABS or Glass Filled Nylon Moulded

Learn more: KSUP Series – Summation Protective Current Transformers

Read related blogs on

Selection of Current Transformers for Metering and Measurement Applications

Customized Current Transformers for Industry Applications

Selection of Current Transformers for Protection Relays or Tripping Relays

Author: Anuradha C

An integral part of the content creation team at KS Instruments, Anuradha is a corporate trainer in the IT/telecom domain with over 18 years of experience. She served in senior technical and management positions in Huawei and TCS for 10+ years