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EV Charging RCD Selection - Revised Safety Requirements 18th Edition T
he 18th Edition Regulations for EV installations Section 722, includes several changes to improve design safety
and performance. One of these changes (722.531.2.101) relates to the selection and use of Type A RCDs with 62196 sockets. Type A can only be used if “the installation incorporates a method of detecting DC residual currents > 6 mA which results in disconnection of the AC supply from the charge point.
Why has this revision been introduced? The 17th Edition Regulations placed the responsibility on the Installer to verify the selection and suitability of the RCD for each installation, based on the amplitude of the DC residual current component related to the vehicle on charge. This value would be determined by reference to the EV Make and Model i.e. Amendment 3 722.531.2.101 stated that;
“…The RCD protecting the charging point shall be at
least type A… If it is known that the DC component of the residual current exceeds 6 mA, then a type B RCD complying with BS EN 62423 shall be installed”.
The wording of the 17th Edition clause, resulted in the
wide spread use of Type A RCDs in EV installations. The charging of vehicles, that produce dc residual currents > 6mA represents a safety hazard for the associated installations.
Meeting the revised Regulation 722.531.2.101 for RCD selection 18th Edition requires the provision of protective measures for DC fault currents for all installations using 62196 sockets; quote the appropriate measures shall be:
RCD Type B or Type A where the installation incorporates a method*
of detecting DC residual currents, >6 mA which results in disconnection of the AC supply from the charge point.
Terminology The terms “Detection” and “Monitoring” are used in the Regulations to differentiate between products that can detect residual currents and “Protection” products that are designed to provide protection i.e. an RCD - see 411.1 Note relating to RCMs and 722.531.2.101 relating to RCD design standards.
3 WINTER 2018/19 | ENERGY MANAGEMENT 2 DRDC-1 IEC62955 Clause 188.8.131.52
Methods for detecting 6 mA DC and disconnecting the supply IEC 62955 specifies the requirements for equipment suitable for the monitoring and detection of DC residual currents in EV charging installations. These devices are collectively referred to as Residual Direct Current Detecting Devices (RDC-DD), not to be confused with an RCD!
See below for details of the various methods for
detecting DC residual currents, proposed in IEC 62955. These should be kept in mind, when reviewing specific EV charge point manufacturers products features + any additional product required to meet the revised installation requirements.
RDC-DDs must meet one of the formats detailed below
and the associated disconnection times specified in the standard, for dc residual current values and non- operating time for AC values. This is to ensure compatibility when using a separate RDC-DD with an RCD.
RDC-M: Monitoring Devices, Units & Modules The three formats proposed for RDC-Ms:
• With mechanical switching built into the unit • Mechanically coupled to a switching unit (RCD, MCB)1 • Electrical output for operation of a control device 2
Note 1: If the associated switching device above, is not an RCD as defined in clause 722.531.2.101, a separate 30mA Type A or F RCCB, RCBO must be connected in series with RDC- M unit.
Note 2: For incorporation within the charge point by the OEM.
RDC-PD: Protection Devices This is a combined format incorporating 6 mA DC detection and 30mA Type A protection in one unit.
This unit can be easily installed or retrofitted in the field, to meet the revised installation requirements.
DFS4 A EV IEC62955 Clause 4.1.2
Doepke u 01628 829133 u www.doepke.co.uk
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