EMP Effects on Protection and Control Systems

Transcription

1 EMP Effects on Protection and Control Systems Copyright SEL 2014

2 Overview EMP description and effects on protection and control systems EMP standards for C4 buildings Present EMC standards and protection for protection and control systems Relays and IEDs in general Panels and Control Houses Cables Possible changes to present design for better EMP protection Testing requirements and preliminary results

3 EMP Threat High Altitude Electromagnetic Pulse (HEMP) Nuclear burst, very high altitude (>30km, effects known since 60 s experiments >400km) High Power Microwave (HMP) or Intentional Electromagnetic Interference (IEMI) Non-explosive weapons, repeatable pulses directed by antennas, much smaller intensity and area

4 EMP Effects and Waveforms Strong Electric and Magnetic Fields Voltages and currents induced on metallic conductors Possible disruption or damage to electric or electronic equipment Simultaneous effects over wide area

5 EMP Effects on Substation Control Houses, Panels and IEDs Similar to harsh electromagnetic events and environments found in power systems Lighting strikes, RFI, HV surge events, strong magnetic fields during short circuits, etc. Possibly higher severity and different frequencies E1 may affect IEDs at the circuit board level and couple with shorter conductors (1-10m), E2 and E3 affects longer conductors and lines (km, several seconds). Biggest concern conductors from substation yard to control building

6 EMP Protection at IED Level Power systems protection and control standards for IEDs are much more robust than commercial or even industrial equipment. Specify highest severity levels listed in present standards Select products that have been designed to exceed these standards

7 SEL-311C Tested at US Army s Picatinny Arsenal in New Jersey RF from 100 MHz to 4 GHz at power levels from 25 to 1000 volts per meter (Mil-Std 461 ask for 50V/m only)

8 SEL-311C at US Army s Picatinny

9 SEL-311C at US Army s Picatinny SEL-311C Analog Measurements During IEMI In Tolerance Out of Tolerance Field Strength (V/m) Frequency (MHz) No damage, out of tolerance may not lead to relay missoperations if applied with best engineering practices

10 Military standards EMP Standards MIL-STD A 1998 High Altitude Electromagnetic Pulse Protection for Ground-Base C4I Facilities Performing Critical Time-Urgent Missions IEC SC 77C

11 EMP Hardening / Enclosure Facility shield / Electromagnetic barrier Faraday Cage: Metallic continuous conductive enclosure closed on all wall, ceiling and floor. Continuously welded, qualified procedures and personal Minimize points of entry (POEs) Equipotential ground plane

12 Control Houses and Systems for EMP SEL has not designed EMP shielded control houses No utility customer requirements IEC standards recently released Present control house design and IED technologies already hardened vs. other types of electromagnetic effects Major design changes would be required to meet HEMP standards Test and validation needs special equipment

13 Present Control Houses Shield Several control house designs provide external metallic shield

14 Present Control Houses Shield Sometimes provide 2 or 3 metallic barriers that attenuate electromagnetic fields (not welded)

15 Control Houses Hardened Shield for EMP Military Std A. Faraday Cage Inside Metal or Concrete Power Core Change of steel gauge and continuously welded

16 EMP Hardening / Enclosure Protection and Control Panels Closed cabinets provide extra shielding for IEDs

17 EMP Hardening / POEs Architectural entryways, two shielded doors, interlocks (or unprotected when open). No windows. Mechanical POE like piping and ventilation Waveguide-below-cutoff

18 EMP Electrical POEs Main threat to substation control rooms, coupling at conductors to yard Each power, communication and control conductor (shielded or unshielded) shall be provided with transient suppression / attenuation devices Surge arresters, filters, non-linear elements, etc Exceptions for conductors on specific conditions of conduit shielding 1-10Amp, 250m (820ft) buried metallic conduit or 31m (102ft) non-buried metallic conduit

19 Cable Entry Protection Mil Std 188

20 Control Houses POEs Modify vents to waveguide-below-cut-off Shielded doors Each conductor protected or each conduit shall be welded to shield Limit number of control conductors entering control building from substation yard

21 Cable Entry Protection Individual Cable EMC protection

22 Transmission Yard Conductors

23 Minimize Electrical Points of Entry Using Fiber Optics Peer to peer technologies available Serial Mirrored Bits / Ethernet GOOSE Process Bus Technologies under development for analog signals (CTs & PTs) Reduce commissioning or substation upgrade time, copper cost, cable trench cost and size and POEs Avoid cable or conduit protection and Current Pulse Injection Test Increase fiber and field cabinet cost, cabinet must be totally closed (NEMA 4) and hardened for EMP with EMC gaskets

24 Hard Wire Process Bus 72 CC for analog inputs 60 CC for discrete inputs Traditional injection testing

25 Fiber Process Bus 7 fiber for analog/discrete or Process bus optional, relays in FTK wired to each CT/PT Traditional injection testing

26 Remote I/O Near Breakers and Transformers

27 Shielding Effectiveness Test

28 Pulse Current Injection Test

29 Cable Entry Protection Testing for conducted current

30 Preliminary Testing to Control House Test with control house as is Only shielding effectiveness test 30 to 40dB average attenuation from 10kHz to 10GHz Conventional doors, cable entries and louvers are the main leakage. 10 to 20db attenuation

31 Summary Understand customer requirements for EMP, review standards for utility applications Use substation hardened IEDs for relays, controls and HMI computers Reduce electrical POEs with fiber optics to reduce yard conduits and their welded connections to control house or individual cable protections Significant costs associated with manufacturing a control building with integrated faraday cage. Specialized test procedure and equipment for MIL standard compliance would be required.