Table of Contents
How do I choose a current transformer?
Important Points for Selecting a CT
- Current Transformer Output.
- Conductor Size.
- Load Size or Amperage Range.
- Accuracy Rating.
- Form Factor.
- Regulatory Requirements.
- Using Rogowski Coils.
What are current transformers used for?
A Current Transformer (CT) is used to measure the current of another circuit. CTs are used worldwide to monitor high-voltage lines across national power grids. A CT is designed to produce an alternating current in its secondary winding that is proportional to the current that it is measuring in its primary.
How do you size a current transformer for protection?
Consider a CT with the following specification and protection requirements:
- CT: 600/1 5P20 15 VA, Rct = 4 Ω
- CT Leads: 6 mm2, 50 m long. – use R=2 ρ l /a to calculate = 0.0179 Ω/m.
- Relay: Siemens 7SJ45, Ktd = 1.
- Short circuit current, Iscc max = 30 kA.
What is current transformer advantage?
Its capability to isolate the high voltage and current to low values ensures safe operations and safe handling of the equipment. Current transformers offer electrical isolation among measuring instruments & high voltage power circuits.
What are two basic types of current transformers?
Current transformers can be divided into two major types,
- Single-turn (bar) primary and.
- Multi-turn wound primary.
Which type of transformer is used in current transformer?
The Current Transformer ( C.T. ), is a type of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary.
What is the difference between power transformer and current transformer?
The power transformer is used to convert voltage using the number of windings in the two coils as ratio, while the current transformer is just an inductor placed around a wire to sense the magnetic field caused by the changing current. So you use it to measure the (AC) current without breaking the circuit.
Where is CT installed?
For correct measurements, CTs must be installed on the phase conductor that corresponds to the voltage input connection. The voltage input connections are on the green, five position, screw terminal block. For example, the ØA CT must be installed on the same phase conductor that is connected to ØA Voltage input.