Remedial Action Schemes / Special Protection Schemes
Remedial Action Schemes (RAS) are designed to monitor and protect electrical systems by automatically performing switching operations in response to adverse network conditions. This ensures the integrity of the electrical system and avoids network collapse.
Typical automatic remedial actions include:
- Generator tripping to reduce energy input to the system
- Load tripping, inserting braking resistors, series capacitors, opening interconnecting lines and system islanding
RAS systems are often applied to large power systems for control of the system during severe abnormal conditions, when traditional localized control is inadequate. Disastrous events such as 9/11, Hurricanes, Tsunamis, and others show that, now more than ever, complete backup RAS control centers are essential to disaster recovery.
These systems are typified by large numbers of diverse communication paths providing real time information from a wide geographic area. The paths are usually a mix of every media available, from lease circuits, to audio circuits, dark fiber, and IP networks.
These communication systems transport data from substations and deliver it in real time to a single site for use by the RAS control computers. Traffic from the control centers to the substations allows control of the power network.
The RAS action is generally performed by a central controller. The controller needs data collected by field units such as our GARD 8000® RAS Module. Field units measure currents, voltages, and/or transducer quantities (W, VAr) and deliver these to the central unit for evaluation and comparison with data from other points in the power system. The GARD 8000® also acts as a remote controller, performing breaker operations via programmable logic and inputs/outputs when a command is received from the central unit.
The amount of raw data in a power system can easily overwhelm the bandwidth available to communicate with the control center. Our RAS module provides ways to reduce the amount of raw data by preprocessing it prior to transmission. Transporting all the raw data only to combine the various values after the data arrives at the control center is inefficient. Doing the mathematical combination and simplification at remote sites, reduces the bandwidth required.
By introducing mathematical capabilities at the measurement sites or substation level, data can be normalized. All the variability in collection methods and sensors is isolated from the control center. Localized changes only need to be normalized to the previously expected values, thereby eliminating any impact on the control center programming.
Featured Product: GARD 8000®
Designed specifically for protection applications, this advanced communications platform provides users with a fully programmable system that can be used for Direct Transfer Trip, Permissive Transfer Trip, Blocking, Unblocking and Phase Comparison applications. One unique flexible platform handles analogue, digital, and Ethernet communications with multiple interfaces combined in one unit. The interfaces can be programmed together or independently, according to the needs of the application.
Features and Benefits
- Modular platform with wide range of functional modules and diverse communications options and fully customizable logic
- Eliminates the need for multiple devices but maintains redundancy requirements for critical applications
- One common platform for a wide range of protection and communications applications reduces the costs associated with maintaining multiple platforms of equipment
- Assures reliability, security, dependability, and low latency for real-time critical applications