Size template. Grid Connection Masterclass Energex John Lansley Senior Network Solutions Engineer

Transcription

1 Size template Grid Connection Masterclass Energex John Lansley Senior Network Solutions Engineer

2 The average system size has doubled since 2010

3 Key Network Issues Reverse power on up to 12 off 11 kv feeders major impact on Regulators Around 100 voltage enquiries per month 40% solar related and remedial work required on 20 distribution substations (typically by balancing the LV network and dropping transformer tap) Remedial costs around $11 Mill per annum High voltage at customer supply points - can cause damage to customer equipment and lead to insurance claims (a $30 K claim where a non solar customer received up to 264 volts) 42 kw of Solar PV s on 100 kva transformer 1200 m of LV cable (240 mm2) 2 x 10 kw, 2 x 4.5 kw and 1 x 5.3 kw Solar PV systems Unbalance volts with one phase up to 264 Volts (at CP) High voltage can cause nuisance overvoltage protection tripping of customer Solar PV inverters leading to customer complaints due to loss of revenue.

4 Energex Connection Standards 1143 Connection guidelines for PV/IES Systems up to 30kVA 233 Connection guidelines for PV/IES systems 30kW 5MW (equivalent to Chapter 5A of NER) 1188 Connection guidelines for embedded generation >5MW (equivalent to Chapter 5 of NER) Location

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7 Assessment Criteria Test 1 11kV Feeder penetration test (15% of 50POE rating) Test 2 Distribution transformer penetration test (25%) Test 3 Unbalanced generation test (S i < 8% nameplate rating transformer) Test 4 HV Disturbance Test (S i / S sc < 0.1%) at 11kV PCC Test 5 LV Disturbance Test (S i / S sc < 1.0%) at LV PCC S i = inverter rating (kva) S sc = short circuit rating (kva)

8 Alternatives Where Test Fails Test 1 & 2 nil export system, reduce size. Test 3 three phase system, reduce size Test 4 & 5 look at customer side mitigation for reducing voltage disturbance (eg. Varying power factor, lower emission inverters) Network side mitigations funded by customer are also options (eg dedicated transformer, HV feeder)

9 Network Solutions to address increasing levels of solar PV penetration Balancing the PV load is an effective action when there are large single phase solar PV systems on the smaller distribution transformers (less than 20 customers). Balancing is less effective on the larger distribution transformers (where there are up to 100 customers) and the loads are better balanced A change in transformer tap will reduce the voltage by 6 Volts (2.5%) this is the main action for addressing high voltage but may not be possible if the customer voltages fall below the regulated limit of V. Generally only one tap-change increment can be accommodated without compromising overall voltage regulation. An upgraded transformer will allow the opportunity to re-set the taps (by 6 volts) and allow higher penetrations of solar PV. This action may not be possible if the pole is not suitable for the additional loads. A new transformer is generally required where the high voltage is caused by long lengths of LV, typically in excess of 600 metres this may be all Energex LV conductors or part Energex and part consumer mains. The cost for a new transformer installation can be considerable if the 11 kv network has to be extended a long distance. Where there are smaller aged conductors (e.g 7/.080 copper) re-conductoring is an option to reduce voltage rise/drop and maintain LV within regulated limits. Modelling indicates that reconductoring 7/.080 with LVABC can halve the voltage rise. Some of the newer technologies (e.g on load tap changer) are expected to cost more than an upgraded transformer, but less than the installation of a new transformer, but others (e.g STATCOM) is expected to be at a similar cost to a new transformer. The STATCOM does have other advantages as it can offset peak load with the use of the battery storage.

10 Calculations Required Where Test 4 & 5 Fail Internal voltage rise Harmonics - ( Hi 3 ) Flicker calculate actual voltage rise at PCC based on source impedance. Ramping of inverters to match load for nil export. I V r IR IX V s

11 Other Items Approved relay list for backup anti-islanding Nil export requirements Inverter settings 257V overvoltage (260V 2 sec) Leave inverters OFF prior to metering being installed Parameter Vmax Vmin Fmax Fmin Disconnect time Reconnect time Setting 257V (260V 2 sec) 210V 52Hz 47Hz 2 secs seconds

12 Design Certification Report (DCR) Network connection diagram Protection line diagram Protection settings Inverter & panel details, incl settings Calculation of internal voltage rise to PCC If fails Test 4 & 5 calculations showing customer mitigation for power quality Test & Commissioning Report (TCR) Steady state voltage log Flicker and harmonics log before & after. Anti-islanding tests OV/UV setting on backup relay pickup test. Signed by a Registered Professional Engineer Qld (RPEQ) Signed by a Registered Professional Engineer Qld (RPEQ)

13 Example 2 Customer applies for 96kVA 3 phase off a shared transformer 315kVA nameplate rating. Source impedance j1.81 ohms on 11kV, Ztr = j15.01 ohms as seen at 11kV terminals. 11kV Feeder CRB15A Min feeder load estimated at 30% feeder load = 646kVA (Max PV penetration = 50% min feeder load). There is already 61kW connected PV to distribution transformer, and 250kVA off 11kV feeder. ENERGEX ASSESSMENT Test Limit Actual Pass/Fail 1. 11kV Feeder Penetration Test 323 kv.a 346 kv.a fail 2. Distribution Transformer Penetration 49.8% Test 25.0% fail 4. 11kV Feeder Voltage Fluctuation & Distortion Test 0.10% 0.24% fail 5. LV Feeder Voltage Fluctuation & Distortion Test 1.0% 0.1% pass ASSESSMENT RESULT FAIL Options Nil export (overcomes Test 1) Dedicated transformer (overcomes Test 2 & 5) Reduce size to pass Test 4 or prove by calculation & customer side mitigation that no quality of supply concerns on HV.

14 Summary Size Assessment Nil Export Backup Protection RPEQ Design RPEQ Testing Assessment Fee 5kW No N/A No No No No >5 to 30 kw Yes Option No No No No >30 to 150kW Yes Option Approved relay, no NVD for nil export >150kW Yes Option Approved relay, includes NVD on HV Yes If fails Test 4 or 5 $ $3000 Yes Yes Actual costs