Manual Gossen Metrawatt PROFITEST MXTRA (page 90 of 96) (English)

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90 GMC-I Messtechnik GmbH

21.2 At which values should/must an RCD actually be tripped?

Requirements for Residual Current Devices (RCDs)

General Requirements

• Tripping must occur no later than upon occurrence of rated re-

sidual current (nominal differential current I

N

and

• Maximum time to trip may not be exceeded.

Additional requirements due to influences on the tripping current range

and the point in time of tripping which have to be taken into consider-

ation:

• Residual current type or waveform:

This results in a reliable tripping current range.

• Mains type and line voltage:

This results in maximum tripping time.

• RCD variant (standard or selective):

This results in maximum tripping time.

Definitions of Requirements in the Standards

VDE 0100, part 600, which is included in all German standards col-

lections for electricians, applies to measurements in electrical sys-

tems. It plainly states: “The effectiveness of the protective mea-

sure is substantiated when shut-down occurs no later than upon

occurrence of rated differential current I

N

.”

As a requirement for the measuring instrument manufacturer,

DIN EN 61557-6 (VDE 0413, part 6) unmistakably specifies:

“The measuring instrument must be capable of substantiating the

fact that the residual current which trips the residual current

device (RCD) is less than or equal to rated residual current.”

Comment

For all electricians, this means that during scheduled protective

measures testing after system modifications or additions to the

system, as well as after repairs or during the E-check conducted

after measurement of contact voltage, the trip test must be con-

ducted no later than upon reaching a value of, depending upon

the RCD, 10, 30, 100, 300 or 500 mA

How does the electrician react in the event that these values are

exceeded? The RCD is replaced!

If it was relatively new, a complaint is submitted to the manufac-

turer. And in his laboratory he determines: The RCD complies with

the manufacturer’s standard and is OK.

A look at the VDE 0664-10/-20/-100/-200 manufacturer’s stan-

dard shows us why:

Because the current waveform plays a significant role, the current

waveform used by the test instrument is also important.

Set residual current type or waveform at the test instrument:

It’s important to be able to select and take advantage of the cor-

responding settings at one’s own test instrument.

The situation is similar for breaking times. The new VDE 0100

part 410, should also be included in the standards collection.

Depending upon mains type and line voltage, it specifies breaking

times ranging from 0.1 to 5 seconds.

RCDs usually interrupt more quickly, but in some cases they can

take a bit longer. Once again, the ball is in the manufacturer’s

court.

The following table is also included in VDE 0664:

Two limit values are highly conspicuous:

Standard Max. 0.3 s

Selective Max. 0.5 s

All of the limit values are already included in good test instru-

ments, or it’s possible to enter them directly and they’re displayed

as well!

Select or set limit values at the test instrument:

Type of Residual Current Residual

Current

Waveform

Allowable Tripping

Current Range

Sinusoidal alternating current 0.5 ... 1 I

N

Pulsating direct current

(positive or negative half-waves)

0.35 ... 1.4 I

N

Phase angle controlled

half-wave currents

Phase angle of 90° el

Phase angle of 135° el

0.25 ... 1.4 I

N

0.11 ... 1.4 I

N

Pulsating direct current superimposed

with 6 mA smooth, direct residual current

Max. 1.4 I

N

+ 6 mA

Smooth direct current 0.5 ... 2 I

N

System

50 V < U



120 V

120 V < U



230 V 230 V < U



400 V

> 400 V

AC DC AC DC AC DC AC DC

0.8 s 0.4 s 5 s 0.2 s 0.4 s 0.1 s 0.1 s

0.3 s 0.2 s 0.4 s 0.07 s 0.2 s 0.04 s 0.1 s

Variant

Residual

Current

Type

Breaking Time at

Alternating

residual

current

1 x I

N

2 x I

N

5 x I

N

500 A

Pulsating

direct residual

current

1.4 x

N

2 x 1.4 x I

N

5 x 1.4 x I

N

500 A

Smooth, direct

residual

current

2 x

N

2 x 2 x I

N

5 x 2 x I

N

500 A

Standard

(undelayed)

or briefly

delayed

300 ms Max. 0.15 s Max. 0.04 s Max. 0.04 s

Selective 0.13 ... 0.5 s 0.06 ... 0.2 s 0.05 ... 0.15 s 0.04 ... 0.15 s

Negative half-wave

Positive half-wave

Waveform:

Negative direct current

Positive direct current

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