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22 GMC-I Messtechnik GmbH

7.3 Testing for Special RCDs

7.3.1 System, Type RCD-S Selective RCCBs

Selective RCDs are used in systems which include two series

connected RCCBs which are not tripped simultaneously in the

event of a fault. These selective RCDs demonstrate delayed

response characteristics and are identified with the symbol.

Measuring Method

The same measuring method is used as for standard RCCBs (see

sections 7.1 on page 18 and 7.2.1 on page 20).

If selective RCDs are used, earthing resistance may not exceed

half of the value for standard RCCBs.

For this reason, the instrument displays twice the measured value

for contact voltage.

Select Measuring Function

Set Parameter – Selective

Start Measurement

Tripping Test

➭ Press the I

ΔN

key. The RCCB is tripped. Blinking bars appear

at the display panel, after which time to trip t

and earthing re-

sistance R

are displayed.

The tripping test need

only be performed at

one measuring point for

each RCCB.

Note

Selective RCDs demonstrate delayed response charac-

teristics. Tripping performance is briefly influenced (up to

30 s) due to pre-loading during measurement of contact

voltage. In order to eliminate pre-charging caused by the

measurement of contact voltage, a waiting period must

be observed prior to the tripping test. After the measuring

sequence has been started (tripping test), blinking bars

are displayed for approximately 30 seconds. Tripping

times of up to 1000 ms are allowable. The tripping test is

executed immediately after once again pressing the I

ΔN

key.

7.3.2 PRCDs with Non-Linear Type PRCD-K Elements

The PRCD-K is a portable RCD with electronic residual current

evaluation laid out as an in-line device which switches all poles (L,

N and PE). An undervoltage trigger and protective conductor

monitoring are additionally integrated into the PRCD-K.

The PRCD-K is equipped with an undervoltage trigger, for which

reason it has to be operated with line voltage, and measurements

may only be performed in the on state (PRCD-K switches all

poles).

Terminology (from DIN VDE 0661)

Portable protective devices are circuit breakers which can be con-

nected between power consuming devices and permanently

installed electrical outlets by means of standardized plug-and-

socket devices.

A reusable, portable protective device is a protective device which

is designed such that it can be connected to movable cables.

Please be aware that a non-linear element is usually integrated

into PRCDs, which leads to immediate exceeding of the greatest

allowable contact voltage during U

IΔ

measurements (U

IΔ

greater

than 50 V).

PRCDs which do not include a non-linear element in the protec-

tive conductor must be tested in accordance with section 7.3.3

on page 23.

Objective (from DIN VDE 0661)

Portable residual current devices (PRCDs) serve to protect per-

sons and property. They allow for the attainment of increased lev-

els of protection as provided by protective measures utilized in

electrical systems for the prevention of electrical shock as defined

in DIN VDE 0100, part 410. They are to be designed such that

they can be installed by means of a plug attached directly to the

protective device, or by means of a plug with a short cable.

ΔN

Type 1: