Photovoltaic system: electrical equipments selection
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Grid connected PV system <= 10kW (Residential)
One single phase inverter
- Typically, a 5kW grid-connected single-phase inverter. with UOC MAX ≤ 600V.
- One or two strings – Isctc < 25A, IAC < 32A.
- In this design there is no string protection.
- A PV main switch is necessary. When the inverter is indoors, an additional remote controlled switch at the DC cable entry point is recommended for emergencies services.
| Needs | String junction box | PV array main switch | Inverter | AC box (400V) |
|---|---|---|---|---|
| Switchgears and control (Q) | ||||
| - Isolation | • | • (d) | (a) | • (d) |
| - Switching (Making & breaking rated current |
• DC21B |
• (d) DC21B |
(a) | • (d) |
| - Control | • (b) | • (d) | (e) | • (d) |
| - Over-current protection | (c) | • (f) | ||
| - Protection against Insulation fault |
(h) | (h) RCD type B or A SI | ||
| Surge protection (SPD) | • type 2 | • type 1 or 2 | ||
| Enclosure (E) | Outdoor Double insulation |
Indoor Double insulation |
Standard AC requirement + grid code requirement | |
| Metering | Inverter relevant parameters | Energy | ||
(a) PV array main switch could be included in the inverter. This solution makes inverter service or replacement more difficult.
(b) Remote switching for emergency services located as closely as possible to the PV modules or to the point of entry of DC cables in the building.
(c) No protection is required when the number of string does not exceed 2.
(d) Service and emergency switching
(e) Inverter shall include a protection for anti-islanding (in accordance with VDE 0126 for example)
(f) Overload and short-circuit protection B curve recommended.
(g) This SPD could be unnecessary if there is another SPD in the AC installation at a distance of less than 10 metres.
(h) If the inverter provides no galvanic separation a RCD protection is necessary on AC side. IEC 60364-712 specifies RCD type B. Some local regulations require RCD type A SI
Fig. P22 : 10-100kW single multi MPPT inverter
10 to 100kW grid connected PV system (Small building)
One three phase multi input inverter without array box
- Typically, 10kW to 36kW grid-connected inverters, UOC MAX probably higher than 600V (i.e. 800V or 1000V), Isctc < 125A, Iac < 63A.
- In this range of power, inverters usually have between 2 and 4 maximum power point tracking (MPPT) inputs, so the number of strings in the same DC sub-network is equal to one or two.
- There is no need for string protection.
- A PV main switch for each MPPT input is necessary.
- When an inverter is indoors, additional remote-controlled switches at DC cable entry point are recommended for emergencies services.
| Needs | String junction box | PV array main switch | Inverter | AC box (400V) |
|---|---|---|---|---|
| Switchgears and control (Q) | ||||
| - Isolation | • | • (d) | (a) | • (d) |
| - Switching (Making & breaking rated current |
• DC21B |
• (d) DC21B |
(a) | • (d) |
| - Control | • (b) | • (d) | (e) | • (d) |
| - Over-current protection | (c) | • (f) | ||
| - Protection against Insulation fault |
(h) | (h) RCD type B or A SI | ||
| Surge protection (SPD) | • type 2 | • type 1 or 2 | ||
| Enclosure (E) | Outdoor IP5x Double insulation |
Indoor IP5x Double insulation |
Standard AC requirement + grid code requirement | |
| Metering | Energy | |||
(a) PV array main switch could be included in the inverter. This solution makes inverter service or replacement difficult.
(b) Remote switching for emergency services located as closely as possible to the PV modules or to the point of entry of DC cables in the building.
(c) No protection is required when the number of string does not exceed 2.
(d) Service and emergency switching
(e) Inverter shall include a protection for anti-islanding (in accordance with VDE 0126 for example)
(f) Overload and short-circuit protection (B curve recommended).
(g) If there is no SPD in the inverter or if the distance between DC box and inverter exceeds 10m a SPD is necessary in this box.
(h)
- If the inverter provides no galvanic separation a RCD protection is necessary on AC side. IEC 60364-712 specifies RCD type B. Some local regulations require RCD type A SI
- If the inverter provides at least simple separation
- Without functional earthing: insulation monitoring is necessary, it's usually done by the inverter in this range of power.
- With functional earthing: the earthing shall be done with a DC MCB breaker (C60PV 4P series 2 – 10A) or a fuse.
Fig. P23 : 10-100kW single multi MPPT inverter
One three phases inverter with One Array box
- Typically, 30kW to 60kW grid-connected inverters. UOC max is generally higher than 600V (up to 1000V), Isctc does not exceed 200A, Iac does not exceed 100A.
- This design has more than 2 strings.
- Reverse current protection is therefore necessary.
- A main PV switch is required. When an inverter is inside, additional remote-controlled switch at DC cable entry point is recommended for emergencies.
| Needs | String / Array junction box | PV array main switch | Inverter | AC box (400V) |
|---|---|---|---|---|
| Switchgears and control (Q) | ||||
| - Isolation | • | • (d) | (a) | • (d) |
| - Switching (Making & breaking rated current |
• DC21B |
• (d) DC21B |
(a) | • (d) |
| - Control | • (b) | • (d) | (e) | • (d) |
| - Over-current protection | • | (c) | • (f) | |
| - Protection against Insulation fault |
(h) | (h) RCD type B or A SI | ||
| Surge protection (SPD) | • type 2 | • type 1 or 2 | ||
| Enclosure (E) | Outdoor IP5x Double insulation |
Indoor IP5x Double insulation |
Standard AC requirement + grid code requirement | |
| Metering | P, Q, PF, Energy | |||
(a) PV array main switch could be included in the inverter. This solution makes inverter service or replacement difficult.
(b) Remote switching for emergency services located as closely as possible to the PV modules or to the point of entry of DC cables in the building. The main switch in array box can be equipped with tripping coil and motor mechanism for remote reclosing for that purpose.
(d) Service and emergency switching
(e) Inverter shall include a protection for anti-islanding (in accordance with VDE 0126 for example)
(f) Overload and short-circuit protection (B curve recommended).
(g) If there is no SPD in the inverter or if the distance between DC box and inverter exceeds 10m a SPD is necessary in this box.
(h)
- If the inverter provides no galvanic separation a RCD protection is necessary on AC side. IEC 60364-712 specifies RCD type B. Some local regulations require RCD type A SI.
- If the inverter provides at least simple separation
- Without functional earthing: insulation monitoring is necessary
- With functional earthing: the earthing shall be done with a DC MCB breaker (C60PV 4P series 2 – 10A) or a fuse.
Fig. P24 : 10-100kW single MPPT inverter
