Technical Application Papers No.10 Photovoltaic plants - ABB

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4 Connection to the grid and measure of the energy 36 Photovoltaic plants Technical Application Papers 4.3 In parallel with the MV network The main device consists of (CEI 0 -16): • a three-pole circuit-breaker in withdrawable version with opening trip unit; • or a three-pole circuit-breaker with opening trip unit and three-pole switch- disconnector to be installed on the supply side of the circuit-breaker. As regards the opening command of the main device due to the intervention of the main protection, an undervoltage coil must be used because if, for any reason, the supply voltage of the main protection lacks, the opening of the main device occurs also in case of absence of the command coming from the main protection. The general protection includes (CEI 0-16): • an overcurrent release with three trip thresholds, one with inverse time-delay I> (overload threshold 51), two with constant time I>> (threshold with intentional delay 51) and I>>> (instantaneous threshold 50); • a zero-sequence overcurrent release 51N with two constant time trip thresholds Io> and Io>>, one for the single-phase earth faults and one for the double singlephase earth faults, or a directional zero-sequence overcurrent release with two thresholds 67N.1 and 67N.2 , one for the selection of internal faults in case of networks with compensated neutral and one in case of insulated neutral, in addition to the zero-sequence overcurrent release with one threshold for the double single-phase earth faults. The interface device can be positioned both on the MV as well as on the LV side. If this device is installed on the MV part of the plant, it can consists of (CEI 0-16 Interpretation Sheet): • a three-pole circuit-breaker in withdrawable version with undervoltage opening release or • a three-pole circuit-breaker with undervoltage opening release and a switch-disconnector installed either on the supply or on the load side of the circuit-breaker 5 . For plants with more PV generators, as a rule, the interface device shall be one and such as to exclude at the same time all the generators, but more interface devices 4 Protection 67N is required when the contribution to the single-phase ground fault capacitive current of the MV grid of the user exceeds the 80% of the setting current fixed by the distributor for the protection 51N. In practice, when the MV cables of the user exceed the length of: • 400m for grids with Un=20 kV • 533m for grids with Un=15kV. 5 The possible presence of two switch-disconnectors (one on the supply side and one on the load side) shall be considered by the user according to the need of safety during maintenance operations. are allowed provided that the trip command of each protection acts on all the devices, so that an anomalous condition detected by a single protection disconnects all the generators from the network 6 . If single-phase inverters with power up to 10kW are used, the interface protection system can be integrated into the converter itself for total generated powers not higher than 30kW (CEI 0-16 Interpretation Sheet). Moreover, since the inverters used in PV plants work as current generators and not as voltage generators it is not necessary to integrate into the interface protection also the zero-sequence overvoltage protections (59N) and the additional protection against failed opening of the interface device (Guide CEI 82-25, II ed.). The interface protection system consists of the functions listed in the Table 4.2 (CEI 0-16 Interpretation Sheet). Table 4.2 Protection Setting value Fault extinction time Intentional delay Maximum voltage (59) ≤ 1.2 Un ≤ 170 ms 100 ms Minimum voltage (27) ≥ 0.7 Un ≤ 370 ms 300 ms Maximum frequency (81>) 50.3 Hz ≤ 170 ms 100 ms Minimum frequency (81
Figure 4.3 Figure 4.4 LV users not enabled for “stand-alone” operation LV users not enabled for “stand-alone” operation Main circuit-breaker (DG) Photovoltaic generator (PV) Main circuit-breaker (DG) Circuit-breaker of the generator (DDG) Three-phase inverter Interface device (DDI) MV network Inverter MV network kWh kWh kvarh 50-51 - 51N - (67N) Main protection PG Interface device (DDI) kWh Circuit-breaker of the generator (DDG) kWh kvarh 50-51 - 51N - (67N) < U 27 - 59 - 81 Three-phase inverter < U Measurement of produced energy Distributor User’s plant 27 - 59 - 81 Main protection PG Interface protection (PI) kWh Interface device (DDI) Circuit-breaker of the generator (DDG) Distributor User’s plant Photovoltaic plants 37 4 Connection to the grid and measure of the energy
Page 1: Technical Application Papers No.10
Page 4 and 5: 2 Index Technical Application Paper
Page 6 and 7: Introduction 4 Introduction Photovo
Page 8 and 9: 1 Generalities on photovoltaic (PV)
Page 20 and 21: 2 Energy production 18 Photovoltaic
Page 22 and 23: 2 Energy production 20 2.4 Nominal
Page 28 and 29: 3 Installation methods and configur
Page 36 and 37: 4 Connection to the grid and measur
Page 40 and 41: 4 Connection to the grid and measur
Page 42 and 43: 5 Earthing and protection against i
Page 44 and 45: 6 Protection against overcurrents a
Page 52 and 53: 7 Feed-in-Tariff 50 Photovoltaic pl
Page 54 and 55: 8 Economic analysis of the investme
Page 60 and 61: 9 ABB solutions for photovoltaic ap
Page 86 and 87: Annex A: New panel technologies 84
Page 88 and 89:
Annex B: Other renewable energy sou
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Annex C: Dimensioning examples of p
Page 98 and 99:
Page 100 and 101:
Page 102:
Page 107:
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