Load Shed Schemes
Load shed schemes are control systems that make automatic adjustments or corrections to the AIES without operator intervention. The primary purpose of load shed schemes are to balance load and generation after a loss of resources, thereby preserving system stability. Load shed schemes are used in the AIES to:
• Provide fast tripping of the BC inter-tie to avoid severe voltage depression or system instability; and
• Stabilize system frequency following disturbances.
Load shed scheme services currently procured by the AESO are required to facilitate imports on the Alberta -British Columbia interconnection. The AESO currently procures two schemes: Import Load Remedial Action Scheme and Load Shed Service.
Import Load Remedial Action Scheme(ILRAS):
ILRAS contracts for interruptible loads that will be automatically tripped following the loss of the AB-BC interconnection during high import levels.
Load Shed Service (LSS):
LSS contracts for loads that will be automatically tripped when the AIES frequency drops to 59.5Hz or below, which may occur when the interconnection trips at high import levels.
The AESO currently has contracts in place with various loads to provide these services.
Load Shed Scheme Resources
AESO Ancillary Services Procurement Process
This document outlines the AESO’s procedure for the procurement of ancillary services
Operating Policies & Procedures (OPP’s) for LSS
The following OPPs make reference to load shed schemes – a brief description of each OPP is listed below. To access each specific OPP please view the OPP table of contents. You will be able navigate from the table of contents to the specific OPPs listed below.
OPP 312: Import Load Remedial Action Scheme (ILRAS) and Load Shed Service (LSS)
To define the policies and procedures for the system controller (SC) in the application of the import load remedial action scheme (ILRAS) and the Load Shed Service (LSS), in order to facilitate increased import capability on the AB-BC interconnection for energy and reserve services.
OPP 301: AB-BC Interconnection scheduling
To define the policies and procedures for the system controller (SC) to carry out when scheduling interchange transactions on the AB-BC interconnection.
OPP 801: Supply Short Fall
To define the procedures for the System Controller (SC) to follow and to specify the measures to be taken by entities involved in responding to generation capacity shortages within the Alberta balancing authority in order to maintain system reliability.