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Figure 9.16.11 Example of surge protective devices in a pitch Figure 9.16.12 Customer-specific testing in the impulse current
system laboratory

overload of the protection components. A stationary condition states, namely yellow (end of service life), green (fully func-
monitoring system allows condition-based maintenance of 10 tional) and red (faulty). If the yellow indicator flag appears, the
BLITZDUCTOR XT arresters. module has reached about 80 % of its service life. In addition
to the visual indication at the module, this signal to replace
Two systems are available: the arrester is also transmitted to the turbine controller via the
1. DRC MCM XT (Figure 9.16.11) – Compact DIN rail moun- remote signalling contact in the next service interval.
ted multiple condition monitoring system for condition mo-
nitoring: Laboratory tests according to IEC-61400-24
IEC 61400-24 (EN 61400-24) describes two basic methods to
¨ Condition monitoring of LifeCheck-equipped arresters perform system-level immunity tests for wind turbines:
¨ Cascaded system permanently monitors up to 150 ar- ¨ When performing impulse current tests under operating
resters (600 signal cores)
conditions, impulse currents or partial lightning currents
¨ Minimal wiring are injected into the individual lines of a control system
¨ Remote signalling via RS485 or remote signalling con- while mains voltage is present. Thus, the equipment to be
tacts (1 break and 1 make contact) protected including all SPDs is subjected to an impulse cur-
rent test.
2. DRC SCM XT – Single condition monitoring system ideally
suited for small-sized wind turbines with max. ten arres- ¨ The second test method simulates the electromagnetic ef-
ters: fects of the LEMP. To this end, the full lightning current is
injected into the structure which discharges the lightning
¨ Condition monitoring of LifeCheck-equipped arresters current and the behaviour of the electrical system is ana-
¨ Monitoring of up to 10 arresters (40 signal cores) lysed by means of simulating the cabling under operating
¨ Minimal wiring conditions as realistically as possible. The lightning current
¨ Remote signalling via remote signalling contact (1 break steepness is a decisive test parameter.
contact)
DEHN offers engineering and test services (Figure 9.16.12)
As is the case with the condition monitoring systems for wind turbine manufacturers such as:
of the BLITZDUCTOR XT series, all arrester systems of
the DEHNguard or DEHNblock series with the addition ¨ Lightning current tests for bearings and gearboxes of the
“FM” can be optionally monitored via a floating contact. mechanical drive string
In case of DEHNguard arresters with the addition “LI“ (Life- ¨ High-current tests for the receptors and down conductors
time Indication), the visual indication indicates three operating of rotor blades

352 LIGHTNING PROTECTION GUIDE www.dehn-international.com