3EK7 Medium-Voltage Surge Arresters — Specifications According to IEC 60099-4

Scope of this specification sheet

This spread from the medium-voltage surge arrester mini-catalog (3EK series) presents the full ratings of the 3EK7 arrester family as specified to the IEC 60099-4 standard. Nineteen catalog variants are listed, spanning rated voltages from 3.0 kV to 60 kV with continuous operating voltages from 2.4 kV to 48.0 kV.

Every variant shares the same core ratings: designation DH, a nominal discharge current In of 10 kA, a charge transfer rating Qrs of 0.5 C, a thermal charge transfer rating Qth of 1.1 C, and a rated short-circuit current Is of 20 kA. The variants differ in housing height (170 mm to 470 mm), which drives the residual voltages, creepage distance, withstand voltages, mechanical load ratings, and weight.

Electrical characteristics

The table gives, per rated voltage, the maximum residual voltages at discharge currents for switching-impulse (30/60 µs at 125 A and 500 A) and lightning-impulse (8/20 µs from 1 kA to 20 kA) current waves. Residual voltage scales essentially linearly with rated voltage — e.g. at the 10 kA / 8/20 µs reference current it ranges from 8.0 kV for the 3 kV arrester to 159 kV for the 60 kV arrester.

Mechanical characteristics

Mechanical data is listed row-for-row against the same 19 rated-voltage variants (the first column below repeats the rated voltage as the row key). Seven housing heights are used across the range: 170, 200, 240, 270, 300, 400 and 470 mm. All variants carry a 20 kA rated short-circuit current. The specified short-term load (SSL) and specified long-term load (SLL) are given both for the arrester alone and when mounted with the insulating bracket; loads decrease with height, from 2940 N SSL (arrester only) at 170 mm down to 1060 N at 470 mm. The insulating bracket is available in short and long sizes; no bracket size is assigned for the 39 kV variant and above.

The lightning impulse withstand voltage (1.2/50 µs) of the housing runs from 104 kV to 281 kV, and the wet power-frequency withstand voltage (1 min) from 49 kV to 131 kV. Approximate weight of the arrester without accessories ranges from 1.5 kg to 5.1 kg.

How to order — type code and accessories

The ordering code is read position by position. Using the example 3EK7 360-4CH4: the prefix identifies the medium-voltage surge arrester family, the digit group gives the rated voltage, and the trailing characters encode the line-discharge class, standard, housing height and shed profile.

Accessories are appended after a -Z suffix, as in the example 3EK7 360-4CH4-Z M11 P12 M81.

Dimensions

The dimension drawing shows the arrester in side and top view. Both the line and ground ends terminate in M12 threaded studs, each protruding 36 mm beyond the housing. The housing height H varies by variant (170–470 mm, see mechanical characteristics), and the silicone sheds have an outer diameter of 119 mm.

Figures & drawings

Click any figure to enlarge.