Know-how
Standards
New standard for PV inverters
IEC 62109-2:2011-06
With the publication of the IEC 62109-2:2011-06 a new edition of the standard is available for the use of inverters in photovoltaic systems.
The full title of the standard is:
Safety of power converters for use in photovoltaic power systems – Part 2: Particular requirements for inverters.
It includes the following requirements for electrical safety:
Residual current monitoring
In case of inverters with a residual current monitoring unit (RCMA) installed, a.c. and d.c. residual currents are to be measured as r.m.s. values.
If the residual current exceeds a value of ≥ 300mA (inverters ≤ 30 kVA) resp. 10 mA per kVA in case of inverters ≥ 30 kVA, the inverter has to be disconnected within 0.3 seconds resp. an appropriate alarm has to be triggered.
In case of a sudden change in the residual current, the following disconnecting times are to be complied with:
30 mA 0,3 s
60 mA 0,15 s
150 mA 0,04 s
Insulation measurement
Before the inverter connects to the mains, the insulation resistance in the photovoltaic array has to be measured.
If the measured insulation resistance is less than R ≤ (VMaxPV / 30 mA) Ω, the inverter must not be connected to the mains.
This insulation measurement carried out before the inverter connects to the mains must not be confused with the requirement for "insulation monitoring during operation of the system" according to DIN VDE 0100-712.
For residual current monitoring, the AC/DC sensitive residual current monitoring module RCMB100 from Bender is available.
Source: www.vde-verlag.de / www.beuth.de
New standard for mobile generators
DIN VDE 0100-551 (VDE 0100-551):2011-06
With the publication of the DIN VDE 0100-551 (VDE 0100-551):2011-06 a new edition of the standard for mobile generators is available.
The full title of the standard is:
Errichten von Niederspannungsanlagen (Low voltage electrical installations) – Part 5-55: Auswahl und Errichtung elektrischer Betriebsmittel (Selection and erection of electrical equipment) – Andere Betriebsmittel (Other equipment) – Clause 551: Niederspannungsstromerzeugungsanlagen (Low-voltage generating sets) (IEC 60364-5-55:2001/A2:2008 (Clause 551); German implementation: HD 60364-5-551:2010 + Cor.:2010.
In comparison to the previous edition from 1997 the requirements for protection by automatic disconnection of supply have not changed substantially. The requirements on the IT system resp. the protective separation are no longer listed in the Annex ZB but instead in the clauses 551.4.4 „Zusätzliche Anforderungen im IT-System“ (Additional requirements in the IT system) resp. 551.4.5 „Zusätzliche Anforderungen bei Schutztrennung“ (Additional requirements for protective separation).
If more than one current-using equipment is connected to the generating set, one of the following protective measures must be applied in order to ensure safe operation:
1) Protective separation with insulation monitoring and automatic disconnection
If the insulation resistance between active parts and the unearthed equipotential bonding conductor drops below 100 Ω per V nominal voltage, the circuits of the current-using equipment shall disconnect automatically within 1 s. Limitation of the network extension and adherence of the requirements for automatic disconnection conditions at the occurrence of two faults are not required.
2) Protective separation with limitation of the length of the wiring system and automatic disconnection
It is recommended that the product of the nominal voltage of the circuit in volts and length, in metres, of the wiring system should not exceed 100 000 V/m, and that the length of the wiring system should not exceed 500 m. The disconnection requirements of VDE 0100-410(VDE 0100-410):2007-06, 411.6.4 shall be fulfilled.
With the insulation monitoring device A-ISOMETER IR423 Bender offers a solution for the protective measure referred to in point 1).
Source: www.vde-verlag.de / www.beuth.de