The choice of RCD type for a charging station is set out in law in DS/HD 60364-7-722 and depends on whether the charging box has approved DC residual current blocking. Type AC is prohibited — and it is not a matter of indifference whether you choose type A or type B.
Introduction
Residual current devices (RCD/HPFI) come in several types and the choice of type is crucial for safety — especially when installing charging stations for electric vehicles. DS/HD 60364-7-722 sets the normative requirements.
RCD type overview
| Type | Recording | Typical application |
|---|---|---|
| AC | Sinusoidal fault current (alternating current) | PROHIBITED in homes and at charging stations in DK |
| A | Sinusoidal + pulsating direct current | Standard in housing; minimum to charging station WITH approved DC blocking |
| F | Type A + certain frequency converters | Installations with frequency converters |
| B | AC + pulsating + smooth DC up to 1000 Hz | Required at charging points WITHOUT approved DC blocking |
When type A — and when type B?
The choice depends on whether the charging box has an integrated and approved DC residual current blocking (RDC-DD):
- 01Ladestander MED godkendt DC-blokering (RDC-DD ≤ 6 mA DC): Type A (eller type F/type A-EV) er tilstrækkeligt.
- 02Charging station WITHOUT approved DC blocking: Type B is required. Type B costs more than type A, but gives full protection against smooth DC fault currents that EV chargers can generate.
- 03Type A alone for charging stations without DC blocking is insufficient protection — regardless of what industry practice may say.
Other requirements for charging station installation (7-722)
- 01Separate circuit — the charging station must not share circuit with other consumers.
- 02Dedicated RCD — not shared with circuits that are not charging stations.
- 03Samtidighedsfaktor = 1 uden belastningsstyring — dimensionér for fuld ladestander-effekt.
- 04With load balancing (dynamic load balancing) a lower factor can be used — see manufacturer documentation.
Cable sizing for charging stations
| Charging station power | Min. Cu cross-section (guidance) |
|---|---|
| 1–3,6 kW | 2,5 mm² |
| 3,6–7,2 kW | 4 mm² |
| 7,2–11 kW | 6 mm² |
| 11–22 kW | 6 mm² * |
RDC-DD: 6 mA DC-detection
Why even talk about DC fault currents? Because an EV charger contains power electronics that in case of a fault can let a smooth (pure) DC fault current leak out. A smooth DC fault current can blind an ordinary type A RCD by saturating its current transformer so it no longer couples reliably on AC faults. There are two legal solutions:
- 01Type B-RCD — detects even smooth DC fault currents and covers the entire spectrum.
- 02RDC-DD (Residual Direct Current Detecting Device) — en vagt indbygget i ladeboksen, der kobler ud, hvis DC-fejlstrømmen overstiger 6 mA. Med en godkendt RDC-DD (≤ 6 mA DC) er en type A-RCD foran tilstrækkelig.
This is the mechanism that determines type A versus type B (see table above). The unit is also called RDC-PD when it is a standalone protective device. (Source: DS/HD 60364-7-722.)
Charging modes (IEC 61851)
DS/EN 61851-1 defines four charging modes based on protection and communication level:
| Fashion | Description |
|---|---|
| Mode 1 | Directly in an ordinary socket-outlet without control/communication |
| Mode 2 | Standard plug socket with control/protection box in the cable (ICCB) — emergency charging |
| Mode 3 | Dedicated charging box with communication (control pilot) — normal AC charging |
| Mode 4 | DC fast charging where the rectifier sits in the stand |
Stiktyper (IEC 62196)
- 01Type 2 (Mennekes) — European standard plug for AC charging (Mode 3), 1- or 3-phase.
- 02CCS (Combined Charging System) — Type 2 extended with two DC pins for fast charging (Mode 4).
Plugs and charging connectors are standardised in DS/EN 62196-1/-2.
1-phase or 3-phase — and phase balancing
A single-phase charger (typically up to 7.4 kW at 32 A) loads only one phase and contributes to phase imbalance. A three-phase charger (11 kW at 16 A or 22 kW at 32 A) spreads the load evenly across all three phases. Distribute several single-phase charging points across different phases, and keep an eye on the Common Regulations' limit for phase imbalance (20 % of the agreed supply capacity, but always up to 16 A and never above 300 A).
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