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» General Information » Immunity » Surge » Surge Test Setup

Surge TEST SETUP From : 61000-4-5 . IEC:1995 +A1:2000

7.1 Test equipment

The following equipment is part of the test set-up :

• equipment under test (EUT);
•auxiliary equipment (AE);
•cables (of specified type and length);
•coupling device (capacitive or arrestors);
•test generator (combination wave generator, 10/700 µs generator);
•decoupling network/protection devices;
•additional resistors, 10 ? and 40 ? (see B.1 of annex B).

7.2 Test set-up for tests applied to EUT power supply

The surge is to be applied to the EUT power supply terminals via the capacitive coupling network (see figures 6, 7, 8 and 9). Decoupling networks are required in order to avoid possible adverse effects on equipment not under test that may be powered by the same lines and to provide sufficient decoupling impedance to the surge wave so that the specified wave may be developed on the lines under test.

If not otherwise specified the power cord between the EUT and the coupling/decoupling network shall be 2 m in length (or shorter).

To simulate the representative coupling impedances, in some cases additional specified resistors have to be used for the tests (explanations, see B.1 of annex B).

NOTE In some countries (e.g. USA) standards for a.c. lines require the tests according to figures 7 and 9 with a 2 W impedance although this is a more severe test. The general requirement is 10 W.

7.3 Test set-up for tests applied to unshielded unsymmetrically operated interconnection lines

In general, the surge is applied to the lines in accordance with figure 10 via capacitive coupling. The coupling/decoupling network shall not influence the specified functional conditions of the circuits to be tested.

An alternative test set-up (coupling via arrestors) is given in figure 11 for circuits with a higher signal transfer rate. Selection shall be made depending on the capacitive load with respect to the transmission frequency.

If not otherwise specified, the interconnection line between the EUT and the coupling/ decoupling network shall be 2 m in length (or shorter).

7.4 Test set-up for tests applied to unshielded symmetrically operated interconnection/telecommunication lines (figure 12)

For balanced interconnection/telecommunication circuits, the capacitive coupling method can normally not be used. In this case, the coupling is performed via gas arrestors (CCITT Recommendation K.17). Test levels below the ignition point of the coupling arrestor (about 300 V for a 90 V arrestor) cannot be specified (except in the case of secondary protection without gas arrestors).

NOTE Two test configurations are to be considered :
• for the equipment level immunity test with only secondary protection at the EUT at a low test level, e.g. 0,5 kV or 1 kV,
• for the system level immunity test with additional primary protection at a higher test level, e.g. 2 kV or 4 kV.

If not otherwise specified the interconnection line between the EUT and the coupling/ decoupling network shall be 2 m in length (or shorter).

7.5 Test set-up for tests applied to shielded lines

In the case of shielded lines a coupling/decoupling network may not be applicable.

Thus the surge is applied to the shields (metallic enclosures) of the EUTs and connected shields of the lines in accordance with figure 13. For shields connected at one end figure 14 applies. For decoupling the connected safety earthwire a safety isolating transformer shall be used. Normally, the maximum length of the specified shielded cable shall be used. With respect to the frequency spectrum of the surge 20 m length of the specified shielded cable shall be used in non-inductively bundled configuration for physical reasons.

Rules for application of the surge to shielded lines:

a) Shields earthed at both ends
• the surge injection on the shield shall be carried out according to figure 13.

b) Shields earthed at one end
• the test shall be carried out according to figure 14. The capacitor C represents the cable capacity to earth and the value may be calculated with 100 pF/m. As a representative value 10 nF may be used unless otherwise specified.

The test level applied on shields is the "line-to-earth value" (2 ? impedance).

7.6 Test set-up to apply potential differences

If it is necessary to apply potential differences which simulate voltages that can occur within a system, the tests may be carried out in accordance with figure 13 for systems with shielded lines, shields earthed at both ends, and in accordance with figure 14 for systems with unshielded lines or shielded lines earthed only at one end.

7.7 Other test set-ups

If one of the specified coupling methods in the test set-up cannot be used for functional reasons, alternative methods (suitable for the special case) shall be specified in the dedicated product standard.

7.8 Test conditions

The operational test conditions and the installation conditions shall be in accordance with the product specification and shall include the:

• test configuration (hardware);
• test procedure (software).

B.1 Different source impedances

• the kind of cable/conductor/line (a.c. power supply, d.c. power supply, interconnection, etc.);
•the length of the cables/lines;
•indoor/outdoor conditions;
•application of the test voltage (line to line or lines to earth).

The impedance of 2 W represents the source impedance of the low-voltage power supply network. The generator with its effective output impedance of 2 W is used.

The impedance of 12 W (10 W + 2 W) represents the source impedance of the low-voltage power supply network and earth. The generator with an additional resistor of 10 W in series is used.

The impedance of 42 W (40 W + 2 W) represents the source impedance between all other lines and earth. The generator with an additional resistor of 40 W in series is used.

In some countries (for instance, USA) standards for a.c. lines require the tests according to figures 7 and 9 with a 2 W impedance; this is a more severe test. The general requirement is 10 W.

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