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In association with:
Speaking of Risks: An Update
to the NRS097-2 and other Technical Requirements
(SSEG)
Background to SSEG
Specification Development
Dr Gerhard Botha
2016/03/31
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Overview
• Background to SSEG in South Africa
• Inverter Specifications
• Small Generator Specifications
• Planning Framework
• Type Testing
• Policies and Procedures
• Installation Standards
• Tariffs
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Background
• Small Scale Embedded Generation
• SA development since 2007
• Municipalities received many requests for solar PVinstallations
• Approached Eskom for unified requirements viaNRS
• First edition published Dec 2010 – Based on IEC61727
• NERSA “approval” of such installations formunicipalities in Sep 2011 – Municipalities need to keep proper records and
report to NERSA, what, where, how much etc.;
– Comply with requirements from NRS 097-2-1;
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Background
• Then happened load-shedding…
• Co-generation
• Tariff
• Requirements – Eskom response via internal
standard• “Distribution standard for the interconnection of
embedded generation”
• Minimum technical and statutory requirements forthe connection of embedded generators tomedium-voltage and high-voltage utilitydistribution networks
• MV and HV
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NRS 097
• Grid interconnection of embeddedgeneration
• Part 1: Distribution standard for the
interconnection of embedded generation – To be based on Eskom standard
• Still undeveloped…
•
>100kVA• SA Grid Code for Renewable Power
Plants (RPP Grid Code)
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NRS 097-2
• Grid interconnection of embedded generation
• Part 2: Small-scale embedded generation
• Section 1: Utility interface
–Technical requirements for a generator toconnect to the utility network
– Not an inverter specification“Device Independent”
– Not a generator specificationInterface Document
– Describe the requirements at the utility interface
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NRS 097-2
• Connected to LV (
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Section 1 New Additions
• Controllability requirements
– Larger than 100kVA
• Ramp-up after abnormal conditions
• Communication requirements
– Need local control
–
Number of installations cannot be individuallycontrolled
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Section 1 New Additions
• Power factor requirements updated
• A1 and A2 pf > 0.98
• A3 pf > 0.95
• May operate anywhere in the shaded region
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Section 1 New Additions
• Safety disconnect requirements
• Abnormal Voltages
Voltage range(at point of connection) Maximum trip timeS
V < 50 % 0,2 s
50 % ≤ V < 85 % 10 s
85 % ≤ V ≤ 110 % Continuous operation
110 % < V < 115 % 40 s
115% ≤ V < 120% 2 s
120 % ≤ V 0,16 s
NOTE If multi-voltage control settings are not possible, the more
stringent trip time should be implemented, e.g. 2 s between 110%
and 120% of voltage.
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Section 1 New Additions
• Safety disconnect requirements
• Abnormal Frequency
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Section 1 New Additions
• Ride-through requirements (Also RPP Grid
Code)
– Category A1 and A2
– Dip type Y and X1 (NRS 048-2)
20s
120%
110%
90%Y
80%
Z1
S
70%
X160%
X2
Z2
40%
T
0%150 600 3000 ms
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Section 1 New Additions
• Ride-through requirements (Also RPP Grid
Code)
– Category A3
– Same as category B (and C excluding Area D)
20s
110%
120%
150 600 3000 ms
40%
0%
60%
Y
Z1
SX1
X2
Z2
T
70%
80%
90%
Area A
Area B
Area C
Area D
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Section 1 New Additions
• Power Quality
• Limits for flicker and voltage unbalance
• Pst = 0,35;
• Plt = 0,30;
• Maximum unbalance between phases
– < 4.6 kVA
– Two- and three-phase connections
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Section 1 New Additions
• EMC
• Smart meter and residential equipment
interference
• SANS/IEC 50065-1
• CISPR 11 Class B
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Section 1 New Additions
• Fault Level
5th percentile of MV
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NRS 097-2
• Section 3: Simplified utility connection criteria for low-voltage connected generators
• For use by utilities – Customers can establish what would be easy to connect,
e.g. smaller than 25% of ADMD/Breaker size
– Maximum size as a function of cable parameters anddistance from transformer
• Flowchart to consider connection without detailedstudies
• When SSEG connection request complies with simplifiedchecks, can be connected
• Principle of fairness
• Eskom would not allow all these connections at this time – Pilot project (dedicated connections)
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NRS 097-2
• VDE 4105 stipulates 3% max voltage
rise due to all SSEG connected
– Implicit in planning flowchart
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Voltage profiles with no generation
Low load1% rise
limit
Peak load
15% drop
limit
105
104.5
109
108
90
90
95
100
105
110
0 5
V o l t a g e ( % )
Distance (km)
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Voltage profiles with generation
105
102
103.5
96.5
105 106.5
112.5
114.5
95
97.5
100
102.5
105
107.5
110
112.5
115
V o l t a g e ( %
)
Distance (km) peak loadlow load
Network can absorb significantly less power than it can supply
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NRS 097-2
• Part 2: Embedded generator requirements – Type Testing
• How to prove the generator complies with requirements ofpart 1
• DRAFT
•
Review international standards again – International exposure• No single document that will fulfil the requirements for SSEG
connection and type testing for LV networks in South Africa• Specific comparison for utility interface:
– VDE 4105
– EN 50438
–IEC 61727, 61000-series, other
– ER G83/1-1 and G59/2
– IEEE 1547 / UL 1741
• Align with international best practices!
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NRS 097-2
• Section 4: Procedures for
implementation and application
• To be developed…
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SA Grid Code
• RPP Grid Code
• Category A – A1: 0 -13.8kVA (4.6kVA/phase)
–
A2: 13.8-100kVA – A3: 100kVA – 1MVA (including smaller units
connected to a dedicated MV/LVtransformer)
• Category B – 1MVA – 20MVA
• Category C – Larger than 20MVA
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SANS: Wiring Code
• SANS 10142-3 WG convened
• Progress slow
– Utility viewpoint
– Installers viewpoint
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Licensing
• Feedback received yesterday
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Safety Concerns
• Installation deficiencies – Installation of utility-accessible lock-out breaker (where feasible)
– Such a breaker is not feasible in shared networks
– DC fed back into network (possible failure modes of the inverter)
– DC vs. AC breakers and associated derating
• Anti-islanding – Failure to disconnect when the network is de-energised
– Test for voltage before work commences will safeguard LV personnel
• Re-connection while maintenance in progress – Failure of the inverter to detect that the network is not energised
– Remains a risk (in shared networks) until LV networks can be earthed
– Earthing at LV requires redesign of LV networks (e.g. providing earthing terminalsetc.)
• LV Maintenance Process –
Need to measure after disconnection – Most voltmeters either DC or AC
• Australia – rumours of several PV installations that caused fires atresidential homes
• Emergency Personnel, e.g. firefighting
2016-04-02 28
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How to earth a
generator
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Few Other Aspects
• No approved tariffs
– Cowboy approach – under the radar
• Offset of consumption
– Gives good return on investment
• Licensing vs. registration
– Regulatory framework
• Power Quality – RPP GC
– Default values for Generators < 5MVA
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Subtleties
• Renewable Power Producers
– Point of Connection
• Embedded Generators
– Generator terminals
– Point of Connection
• Safety aspects
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Conclusions
• South Africa has learnt a lot
• Alignment with international best
practices as far as possible
• BUT: South African Networks and
Conditions are completely different to
typical European or American networks
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Thank you
+27 83 407 9651