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Current Transformer Secondary Over-voltage Protection Device (JZCT)

2018-04-09 14:19

Product Introduction

Current transformer (CT) is widely used in power system for a measurement and control. Secondary load impedance is very small and secondary output voltage is very low in the normal operation of the current transformer, Which is equivalent to a short-circuit operation of the transformer, the secondary full-scale current generally in 1A or 5 A, rated load capacity of 5VA~100VA, the corresponding load resistance of 0.2Ω~20Ω and the secondary voltage is 1V-20V. If secondary windings are open, or primary windings flow through abnormal over-current (such as lightning current, resonant overcurrent, capacitor charging current , inductor starting current, etc.),which will generate thousands of volts or even tens of thousands of overvoltage the secondary side. Which not only endanger the secondary system insulation, but also causes the transformer to burn down and even endanger the life safety of the operation personnel.

Product Usage

♦Widely used in electric power system for indoor high, medium and low voltage switchgear current transformer, outdoor current transformer, box-type substation current transformer and other current transformer sites.

♦Applied to the differential winding, over-current winding, measuring winding, busbar protection winding and standby winding of CT secondary side.

Performance Index

Normal leakage current IL20V: ≤0.5mA

Conductive voltage UC: 100V~200V

Conductive time TS: 5~10ms

Alarm contact capacity: AC 220V/5A

Protection contact capacity: AC 220V/5A

Life: 20000m times action

Protection current: ≥5A

Functional Features

♦Strong anti-interference ability.

♦Multi-Signal output: alarm relay output, latching differential protection output.

♦The input impedance is infinitely large.

♦Industrial design, reliable performance.

♦Signal input and signal output are fully optically isolated.

♦Secondary protection voltage can be set for prenatal reservations.

♦Easy troubleshooting.

♦Manual button reset and automatic reset, convenient for users to choose.

♦Meet on-site installation requirements, rail-mounted, easy to view and debug.

Demonstration of the type

Appearance and install action dimensions


No. of windings

Outer Dimension




Length:117 Width:91 Height:73

Din-rail type



Length:117 Width:91 Height:73



Length:145 Width:91 Height:73



Length:145 Width:91 Height:73

Irfp aterminal wiring instructions

Installation, field test and maintenance


The protective device should be as close to the protected CT as possible and convenient for inspection. Using sheathed cable as long as possible to prevent breakage.

Field test

A multi-meter is used to test its insulation resistance value, which is about 200 KΩ or more.


No maintenance is required for any type of JZCT. 

It can be inspected once a month and tested every four years.

Ordering instruction

All product hole-size drawings need to be confirmed at the time of production.

Terminal changes due to product upgrade, please confirm the terminal diagram when you place an order. 

The above products are standard type configuration, if there is a special order, it is necessary to communicate with the technical department in advance for the transformation of the product.

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