Domestic Load and Firm Load Shedding

1
Domestic Load and Firm Load Shedding

• Phil Lucas

2
Issue

• Exercise Minsk (2006).
• Identified that a number of Large Firm Supply
  Points (gt732,000kWh) comprised domestic load.
• Examples district heating schemes central
  boiler.
• Such Supply Points are currently subject to third
  stage of Firm Load Shedding (Q3.5.1(c)).
• Suggestion that domestic load should not be
  subject to this stage of Firm Load Shedding.

3
Considerations

• Prime Duty on Transporter maintain pressure in
  the network in the event of an emergency.
• Achieved by rapid reduction of large loads
• Any load excluded increases potential for network
  failure.
• Only recognised exception is Priority Consumers

4
Gas Safety (Management) Regulations 1996

• Safety Case requires Transporter to define
  sequence of supply discontinuance taking account
  of risk to consumers.
• Likely to require a hierarchy approach.
• Should be based on Objective Engineering
  Principles
• pressure maintained in network as far as
  possible.
• Reduce load as quickly as possible.
• Avoid Priority Consumers greater risk if turned
  off.
• Risk
• not associated with absence of heating/hot water
  alternative means are supplied to mitigate this.
• is associated with ability to switch off and
  safely reconnect. Central boiler will be
  restarted by a qualified person.
• Drives contents of Emergency Procedures and
  Safety Cases.

5
UNC

• Section Q reflects Emergency Arrangements in
  Safety Case and Emergency Documents (E1/E2)
• Inappropriate for change to emergency
  arrangements be triggered by UNC.
• UNC change would therefore only be triggered by
  material change to Safety Cases.
• Change required to
• NEC Safety Case
• All DN Safety Cases
• Resultant amendments to E1/E2
• National Grid view is that HSE unlikely to accept
  Safety Case changes taking account of
  Transporter primary duty to minimise extent and
  duration of emergency.

6
Priority Consumers

• Only recognised exclusion from normal firm load
  shedding arrangements.
• Determined by Ofgem / DTI
• Consultation currently open on Priority Consumer
  Categories
• Close out 20 October 2006
• Most appropriate route to pursue exclusion from
  Firm Load Shedding stage three.

7
Summary

• Emergency Procedures/Safety Case tailored to meet
  GS(M)R obligations.
• Priority Consumers are the only recognised
  exclusion from normal firm load shedding
  arrangements.
• UNC reflects Emergency Procedures and Safety
  Case.
• UNC should not instigate change.
• Material change to Safety Cases unlikely to be
  approved by HSE.
• Consultation currently open on Priority Consumer
  Categories
• Close out 20 October 2006
• Is the most appropriate route to pursue exclusion
  from Firm Load Shedding stage three.