Slide 1. New Delhi India Oct CIGRE AORC Meeting New Delhi October 2017

Transcription

1 Slide 1 CIGRÉ AORC Panel B1 Insulated Cables Victorian REFCL Program Update (Rapid Earth Fault Current Limiter) Russell Wheatland : Principal Engineer - Asset Management CIGRE AORC Meeting New Delhi October 2017 New Delhi India Oct 2017

2 REFCL Program Update Where it all began Victorian Regulations REFCL Principles REFCL Zone substation components Operation Network Parameter Challenges Current Program status Slide 2 New Delhi India Oct 2017

3 REFCL : Where it all began Dry Lightning The crime of Arson Black Saturday Feb 2009 Slide 3 New Delhi India Oct 2017

4 REFCL : Where it all began Black Saturday Feb 2009 Slide 4 New Delhi India Oct 2017

5 REFCL : Where it all began Black Saturday Feb people lost their lives 2,100 homes were destroyed 1,100,000 acres of land burnt Over 5,000 volunteer firefighters Over 400 separate fires Slide 5 A Royal Commission was established to learn what went wrong and how not to let this happen again New Delhi India Oct 2017

6 REFCL Introduction What are the Regulatory Requirements? The Electrical Safety (Bushfire Mitigation) Regulations 2013 including REFCL specific requirements to: Install REFCLs at 22 ZSS staged over 7 years in 3 defined Tranches. detect and compensate for 22kV earth faults down to 0.5A or less prove that the REFCL operates as per the regulatory REFCLs will be installed at 22 zone substations over 7 years. The order of Slide requirements 6 annually prior the Tranches was determined through a risk based assessment.

7 REFCL Introduction Where is the REFCL Installed? The ZSS transforms from 66kV to 22kV. Slide 7 500kV* or 220kV 66kV 22kV 415 or 240 V The REFCL is installed in a Zone Substation (ZSS). It works by constantly monitoring the surrounding 22kV high voltage powerlines to detect if there

8 Earthing Summary Types of Earthing Earthing technology advancements have reduced fault current and speed of protection over time. Earthing Typical Fault Speed of Treatment Current Protection Solid Earthing 10,000A sec Low Resistive Earthing (NER) 1,000A sec Resonant Earthing (ASC) < 25A <0.1 sec Enhanced Resonant < 0.5A <0.1 sec Earthing (GFN) Slide 8

9 Earthing Technology How Does Resistive Earthing Work? Resistive Earthing Slide 9 Earth Fault Current Moderate Energy Typical fault current = 1000 Amps Following large fires in 1983 most rural ZSS had a Neutral Earth Resistor installed which reduced the fault energy but could still start a fire. 9

10 Earthing Technology How Does Resonant Earthing (Arc Suppression Coil) Work? Zone Substation Powerline Transformer Arc suppression coil (ASC) Earthing Ground / Earth Slide 10 Ground / Earth Earth Fault Current Low Energy Low Energy Typical fault current = <25 Amps The introduction of Resonant technology in Europe c.1917 further reduces energy: This is new to Australia as Resonant technology was not used in

11 Earthing Technology How Does Enhanced Resonant Earthing (GFN) Work? Earth Fault Current Slide 11 The REFCL limits the amount of energy released within milliseconds thus significantly reducing the possibility of a fire being started.

12 Earthing Technology An Earth Fault on a Network with a REFCL Enhanced Resonant Earthing When an earth fault occurs with the REFCL, within milliseconds, the fault is Slide 12 detected and compensated for with a clear absence of sparking.

13 GFN Components What is a Ground Fault Neutraliser (GFN)? A GFN is the type of REFCL technology currently being installed at AusNet Services substations. A GFN consists of 3 components Slide 13 New Delhi India Oct 2017

14 GFN Components Arc Suppression Coil (ASC) The ASC is connected to the power transformer 22 kv neutral and is located in the switchyard The ASC compensates for the capacitive earth fault current leaving only a low residual fault current In order to compensate for the capacitive current the ASC must be tuned to the network Tuning Capacitor Cabinet Inductor Slide 14 Connection from Residual Current Compensator

15 REFCL Fault Detection & Confirmation Fault Condition For a phase to ground fault on the network, the phase to ground voltage of the faulted phase is brought near to zero volts. The phase to ground voltage of the other two un-faulted phases increase to the full phase to phase value which is typically around 22kV. The ASC is used to compensate for the capacitive fault current which forms the bulk of the fault magnitude. The RCC neutralises the remaining residual fault current by injecting current into the arc suppression coil at 180 out of phase of the residual fault current. The magnitude of the residual fault current is typically less than 0.5 Amps. Slide 15 New Delhi India Oct 2017

16 Fault Detection & Confirmation Fault Confirmation Soft Fault Confirmation Example RCC Fault Confirmation steps Fault Detection ASC Example above is for a fault on red phase. This is a typical behaviour of the GFN. Continuous improvement and optimisation will change this slightly Slide 16 The fault current is reduced from 1500A to practically 0 within 60ms with no arcing. High impedance faults can now be detected No trip for transient faults Faulted phase at nearly 0V. Other 2 phases potentially at 24.2 kv

17 Slide 17 REFCL Operation Capacitance Balancing Network capacitance is important so that fault currents of <0.5 A can be detected Any imbalance decreases the sensitivity of the GFN. This means when the REFCL is monitoring the 22 kv lines for faults it must see that the capacitance of all 3 phases of 22 kv powerlines are the same Our target level of imbalance is <0.1 A. Network capacitive imbalance decreases the sensitivity of the GFN.

18 REFCL Operation Capacitance Magnitude The GFN compensates for the capacitive fault current of the line, the overall capacitance of the line is critical in determining how many lines a single GFN can protect. It is hoped that each station can be protected with a single GFN, to limit the implementation costs. As more overhead lines are transferred to be underground cables, this exponentially increases the overall line capacitance. To limit this increase we have introduced a 22kV Low Capacitance cable aka a 33kV insulated cable but marked as 22kV LC The LC cable looks like and is terminated & tested as 22kV cable Implementing into works practices & store system has been challenging Slide 18 Of course, this is only a stop-gap measure and eventually multiple GFNs

19 Current Program Status One ZSS site commissioned in service 6 months Further 2 sites operational and existing site upgrade by summer 17/18 Further 6 sites by May 2019 Extensive program of Line works Suspect Surge arrestors replacement program Slide 19 Network Hardening checks and asset replacements New Delhi India Oct 2017

20 REFCL : Summary Being implemented as a result of the Royal Commission investigation into Victoria s worst bushfire Based on technology that has been widely used in Europe for many years AusNet has lowered the residual current to <0.5A Already installed and running at one site Another two by Feb 2018 Major impact on asset replacement program Older Slide 20 New Delhi India Oct 2017

21 REFCL : Summary Slide 21 New Delhi India Oct 2017