protection and safety of people, the lv network, dg systems … grid conf presentation… · ·...

Protection and Safety of People, the LV network, DG systems and Home

Presenter: Associate Professor Nirmal Nair GREEN Grid Conference 2016 Renewable Energy and the Smart grid 10th February, MBIE, Wellington

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Overview: Contrasting Protection practices of

Generation/Transmission with Distribution/DG

Identifying challenges associated with

protection and safety of Distribution network assets with DG/IES

Steps towards NZ wide guidelines for

Safety and protection for interconnection of

DG/IES to LV Distribution network

Steps towards NZ wide guidelines for Protection and Automation of MV Distribution networks

with DG/IES

Ongoing work: GREEN Grid interconnection

platform, Fault Location Isolation and

Service restoration (FLISR) and Voltage control in LV and MV

with DG/IES

Presentation Flow

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Ref: NIST (2012)

Asset and network flows that need Safety and Protection

http://www.sgip.org/Smart-Grid-Conceptual-Model-Domains

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Existing Protection and Automation for Transmission/Generation Infrastructure

• Bidirectional power flows in normal operation and during faults • ICT for operations and protection of transmission/generation assets • Established guidelines for safety of substation assets & operational protection • Fault analysis and service restoration practices mission critical globally


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Existing Protection and Automation practices for MV/LV Distribution infrastructure

• Unidirectional flow of power during normal and fault • Predominantly no ICT for protection and very limited ICT for automation • Time-coordination of protection elements through pre-defined settings • Fault analysis methods and service restoration focus is primarily local


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Need for revisiting Safety and Protection in Homes & LV/MV distribution

• Safe installation of various Inverter based Energy System (IES) in homes, buildings, industries • Bidirectional flows of power in LV/MV network during normal and fault • Revisiting time-coordination of protection (line crew safety, upstream HV operations security)


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Unidirectional power flow in existing Distribution network

Normal operating condition

Reference: Babak E, Impacts of the Distribution System Renewable Energy Resources on the Power System Protection, IEEE PES Transmission & Distribution Conference & Exposition,2014

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Unidirectional fault current flow in existing Distribution network

Fault or short-circuit situation

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Short circuit of appliance

Protection coordination for unidirectional flow of fault current without DG.

• Time-current coordination to ensure operational selectivity • Failure of primary protection results in backup with increased outage footprint

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Impacts of DG on LV/MV distribution network during normal power flows

• Bi-directional power flow in distribution network under normal operation.

• Potential situation of localized voltage rise

causing safety issues.

Over voltage issue with interconnection of distributed generation- Safety!!!

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Effect of sustained overvoltage on home appliances

Short circuit current fed both from upstream and the DG

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Impacts of DG during fault current flow in Distribution network

Fault current changes due to interconnection of DG

Local and global Protection issues with interconnection of DG/IES

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Miscoordination of Protection devices

No communication between devices

Islanding of DG/IES- Safety issue

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Poses electrical hazard for maintenance crew and public nearby the fault

Protection and safety zones based on Asset location

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Three adjacently overlapping zones of protection & automation: • Home zone, ensuring IES complying with installation and operational standards

• LV zone, evaluating fuse-recloser coordination and transformer protection • MV zone, evaluating consistent DG/IES protection schemes with bidirectional fault flows

This presentations’ focus

GREEN Grid Project Steps undertaken to address safety and protection associated with penetration of DG/IES to NZ homes and distribution networks

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Survey of NZ distribution network ICT infrastructure

Survey protection practices for NZ distribution utilities

Existing DG protection requirements for NZ distribution utilities

Fault behaviour and understanding settings of IES in LV through testing

Pathway chosen for classifying the safety & protection based on voltage and asset class

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Safety and protection guideline

Safety requirements

Installation of DG/IES

Operation of DG/IES

Protection requirements

Protection requirement for LV

Protection requirement for the DG/IES rated up to

10 kVA

Protection of the DG/IES

Protection of the grid

Protection requirement for the

DG/IES above 10 kVA

Protection of the DG/IES

Protection of the grid

Protection requirement for MV

Protection of DG/IES Protection of grid


Safety and protection survey of distribution utilities in NZ

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• A survey of the distribution network protection

technologies and practices by NZ distribution network utilities conducted during 2013-2014.

Section 1- Utility General Information (4)

Section 2- Considerations (3)

Section 3- System Data (14)

Section 4- Phase Protection (4)

Section 5- Ground Protection (8)

Section 6- Reclosing (9)

Section 7- System Faults (7)

Section 8- Cold Load Pickup (6)

Section 9- System Operation (31)

Section 10- Single Wire Earth Return (SWER) (5)

Section 11- Distributed Renewable Generation (4)

Survey of ICT used in NZ distribution networks

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Communication technologies Communication networks Technologies used by NZ utilities Comparison with other countries Applications and requirements NZ future scope

• Joish, H. S. J., Bahadornejad, M., & Nair, N. K. C. (2015). Smart Grid ICT infrastructure: New Zealand perspective. Electricity Engineers Association (EEA) Conference. Wellington, New Zealand.

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Protection and Automation of MV networks with Inverter based Energy System (IES)

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Safety and protection report for interconnection of IES to LV network

Fault characterisation of Inverter based DG (IES)

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• Fault characterization is required to quantify

possible impacts of IES on distribution network. • Various control modes of the inverter required for

grid support needs to be tested, with focus on voltage control for safety.

• Anti-Islanding functionality of the inverter for

safety of grid operation. • Robustness/compliance with standards like NZS

4777.2-2015 to ensure coordination amongst all the IES across the network

Fault characterisation of Inverter based DG (IES)

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EPE centre, UC PSG, UoA

Fault characterisation of Inverter based DG (IES) : Fault current

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• Characterizing fault current involved voltage dips of up to 10 V to emulate severe faults.

• Test shows fault to be a spike of 4 times rated current. • Spike only for 1/40th of a cycle. • Short circuiting line to neutral also generates similar responses

from inverters.

Mishra, A., Santos-Martin, D., Bahadornejad, M., Nair, N. K. C., & Wood, A. R. (2015). Characterization of inverter fault current and LVRT properties. Paper presented at Electricity Engineering Association (EEA) Conference, Wellington, New Zealand. 24 June - 26 June 2015

Fault characterisation of Inverter based DG (IES) : LVRT properties

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• LVRT required to evaluate system wide impact of grid anomaly and inverter disconnections.

• LVRT of different models were obtained so as to

tailor specific LVRT needs. • Can be modified by change in disconnection time.

• Some inverters found to break compliance with

4777.2 when disconnection times changed.

Fault characterisation of Inverter based DG (IES) : Control modes impacts for voltage safety

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0.00E+00

5.00E+01

1.00E+02

1.50E+02

2.00E+02

2.50E+02

3.00E+02

3.50E+02

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12

71

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51

69

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31

97

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Power and current vs Voltage, Voltage-VAR mode

Volatge Active Power (KW/10) Apparent Power (KVA/10) Current (A*10)

• Capability to maintain voltage is important for IES/home zone safety.

• Most inverters with capacity greater than 3KW have

grid support modes. • The modes include control of reactive and active

power with change in voltage and frequency. • NZS4777.2 (2015) needs inverters to have DRM

modes available for quick access to control modes

Relevant standards identified for safety and protection guidelines in LV and MV

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AS/NZS 4777 (2015) Grid connection of energy via inverters

IEEE 1547 VDE-AR-N 4105, BDEW 2008

4777.2 (2015) covers the protection and safety requirements set out in:

AS/NZS 3112 Approval and test specification- plug and socket outlets

AS/NZS 3000 Electrical installations (Australian/New Zealand wiring rules)

AS/NZS 5033 Installation and safety requirements for PV arrays

AS/NZS 1768:2007 Lightning Protection

IEC 62109 Safety of power converters for use in photovoltaic power systems

IEC 62109-1 Part 1: General requirements

IEC 62109-2 Part 2: Particular requirements for inverters

AS/NZS 60335 Household and similar electrical appliances-Safety

AS 62040.1.1 Uninterruptible power systems (UPS): Part 1.1: General and safety requirements for UPS used.

IEC 62052.11 Electricity metering equipment (AC): General requirements, tests and test conditions. Part 11: Metering equipment

SR 2010/36 Electricity (Safety) regulation 2010.

IEC 61850 Communication standard for electrical substation automation systems

Evaluation of LV feeder protection schemes with bidirectional fault flows

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Test case for Home zone protection and fuse MCB coordination

Evaluation of MV protection schemes with bidirectional fault flows

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MV case study and faulty relay operations due to DG

Known issues with DG on distribution network are: • Protection device blinding • Erroneous tripping • Sympathetic tripping

Prime cause is uncoordinated bidirectional fault current flows.

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Recommended Safety and Protection guidelines for interconnection of IES to NZ LV network


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Under Review by GREEN Grid Network Analysis Group

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Power limitation based on hosting capacity and transformer penetration level


Safety requirement – Lightning & Earthing protection

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• Lightning protection system(LPS) as per AS/NZS 1768 and NZS 5033

• Earthing practices as per section 5.3 of NZS 4777.2(2015) and NZS 3000

Protection of the IES

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Automatic disconnection device

• Automatic disconnection device

shall protect the inverter from the grid related faults/abnormalities as set by the NZS 4777.2(2015)


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Protection of the LV grid

Protection of the grid for the faults contributed from IES

• Various protection schemes based on active as well as passive anti-islanding settings are recommended.

• Power limiting device* settings

are also recommended** based on the transformer penetration limit/hosting capacity *( separate protection relay/four quadrant power meter with programmable

logic controller (PLC)/approved inverter with the ability to adjust net power export to zero) ** Non-Export or Limited Export


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Safety and protection recommended guideline for interconnection of IES to NZ LV network

This presentations’ focus was Home zone

Guidelines for Above 10 kVA in LV

Proposed DG connection to LV network

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Operational impacts of bidirectional fault flows for MV protection from both upstream (HV) and downstream (LV)

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• Protection setting impact • False tripping • Sympathetic tripping • Blinding of protection

• Impact on service restoration • Dedicated transformer protection • Coordination with upstream Auto reclosers • Coordination with AUFLS

Auto-recloser coordination

Typical transformer protection

Proposed GREEN Grid Interconnection Platform

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• Disconnect switch • Voltage protection

• Over voltage (59 O) • Under voltage (27 U)

• Frequency protection • Under Frequency (81U) • Over frequency (81O)

• Loss of Main • ROCOF (81R) • Vector shift (78)

• Earth fault and NVD Protection • Earth fault (50N/51N, 50G/51G) • Earth fault Directional (67N/67NC,) • NVD (59N)

• Over Current voltage restraint protection (51V) • Synchronization (25) • Trip supply supervision relay (94) • Power factor or voltage regulation equipment(55) • External system phase unbalance (46) • Directional power for inverter shedding (32) • Fault interrupting devices (AFCI) • Anti _Islanding protection (AS/NZS 4777.2) • SCADA visibility status

AutoCAD concept drawing of proposed GREEN Grid Interconnection platform

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Assessing ICT based Transmission protection, multi-functional, multi-vendor schemes for testing of newer ICT

based distribution based schemes grid

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o Intelligent Electronic Device (IEC) based protection

testing involving ICT based schemes

o Implement conventional transmission protection

scheme and enhance utilising IEC 61850

o Test for multi-vendor interoperability and relay

multi-functionality

o Develop strategies for effective tripping times of

relays and incorporate special protection and

automation into known schemes

Some Features

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o Synthetic generation of waveforms for secondary

injection using commercial facilities

o Simulation of real-time fault events by playback

of recorded COMTRADE files

o Testing of multiple relay schemes using time

stamped waveforms (can be adapted to emerging

network clock implementation)

Software platform for integration of IEC61850

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o Requires seamless integration

of IED software from various

devices and vendors

o Knowledge of IEC 61850 global

best practices for substation

automation in HV

o Keep abreast of the

developments for MV and LV

Service Restoration Guidelines with DG/IES: Ongoing work

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FLISR – FAULT LOCATION, ISOLATION AND SERVICE RESTORATION

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Coordinated voltage control methods for NZ distribution following renewable DG at medium, LV and household levels

Ensuring safe operational voltage at all times for distribution network with DG/IES: Ongoing work

Vectors Residential PV-Battery clusters

The GREEN Grid interconnection box, will be helpful to assess coordinated voltage control strategies using existing and newer voltage control devices with the objective being safe and secure operation at all times (normal and faults).

Summary

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Overview: Contrasting Protection practices of

Generation/Transmission with Distribution/DG

Identifying challenges associated with protection and safety of Distribution network assets with DG/IES

Steps towards NZ wide guidelines for Safety and protection for interconnection of DG/IES to LV Distribution network

Steps towards NZ wide guidelines for Protection and Automation of MV Distribution networks with DG/IES

Ongoing work: GREEN Grid interconnection platform, Fault Location Isolation and Service restoration (FLISR) and Voltage control in LV and MV with DG/IES

Protection of High Voltage substation

and network contrasted with

existing MV/LV feeder predominantly radial

without ICT and DG/IES systems

Bidirectional normal & fault flow reviewed,

Different protection and safety issues with

DG/IES identified

Analysis on effect of DG/IES on LV and MV network conducted

Inverter fault response captured

through tests

Guidelines for interconnection of DG/IES in LV

framed

Modelling analysis on understanding effect of DG/IES on LV and MV

network

Survey NZ distribution utilities:

ICT technologies/ practices, MV

protection devices/ schemes, MV

connected rotating DG protection

guidelines

Guidelines for interconnection of DG/IES in MV

framed

GREEN Grid interconnection box under design and IEC 61850 based testing

Coordination existing MV protection devices, and

upstream AUFLS devices identified

Guidelines presented primarily for DG/IES less than 10 kVA

Extra Slides for any Q&A regarding greater than 10 kVA or MV connected IES/DG protection & automation guidelines

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Connection of small scale inverter based DG rated above 10kVA connected to LV

network

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Backup protection requirement for interconnection of IES/DG above 10 kVA to LV network

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Protection and Automation of MV networks with Inverter based Energy System (IES)

Proposed DG connection to MV network

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protection and safety of people, the lv network, dg systems … grid conf presentation… · ·...

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