Combined CT-PT Metering Unit for Outdoor Installations ( 11KV – 33KV )

Technical Specification As Per IS:2705 & IS:3156


General Particulars



Highest System Voltage( H.S.V.)

12 KV ( r.m.s.)

36 KV (r.m.s.)

Power frequency dry/ wet withstand voltage on primary winding for one minute

28 KV ( r.m.s.)

70 KV ( r.m.s.)

Lightning Impulse withstand voltage (1.2 x 50 μs

75 KV ( r.m.s.)

170 KV ( r.m.s.)

System Particulars



3 Phase 4 Wire with Isolated / Floating neutral as well as solidly earthed

3 Nos. CTs & 1 No. 3 - Phase PT
3 Nos. CTs & 3 Nos. 1 - Phase PT

3 Phase 4 Wire with Isolated / Floating neutral as well as solidly earthed.

2 Nos. CTs & 1 No. 3 - Phase PT
2 Nos. CTs & 3 Nos. 1 - Phase PT

Specific Particulars


Short Time Thermal Current (Ith)

As per customer requirement.
In general CT is to be specified with STF of 100 for 1 Sec. or STC (lth) equal to the system fault level whichever is lower. KA ( r.m.s. )


10 VA to 100 VA for VT
5 VA to 30 VA for CT

Accuracy Class

0.2S, 0.2, 0.5S, 0.5, 1.0 for CT. 
0.2, 0.5 & 1.0 for VT


Secondary Current (CT)

1 Amp or 5 Amp


Secondary Voltage (VT)

110 Ph-Ph or 
110/v3 V, Ph-Neutral

Primary Current (CT)

As per customer requirement.

Primary Voltage (VT)

11KV, 22KV, 33KV for 3-Phase VT
11/v3, 22/v3, 33/v3 for 1-Phase VT

Constructional / Salient Features

Tank is made of mild-steel. Their external surface is painted with one coat of primer and two coats of synthetic enamel paint or hot dip galvanized as per customer requirement. Their internal surface is painted with two coats of oil insoluble paint.
Porcelain bushings conforming to IS: 3347 are mounted over tank – 5 nos. in 3-phase 3 wire and 6 nos. in 3-phase 4-wire metering units
Insulation is dried out by heating in vacuum. Dried and degassed oil conforming to IS:335 is then filled in the transformer under vacuum.
These units are hermetically sealed and have weather proof secondary terminal box, prismatic oil level gauge & pressure release device for release of abnormal pressure making it hazard free.
Each transformer undergoes the entire routine test before dispatch and is delivered safe at site.
These units are suitable for pole mounting as well as platform mounting.
Secondary terminal box is provided with seal making the unit pilfer resistant. Additional seal/s can also be provided as per customer requirement on main tank or on identification plate etc.