PROCESO DE ELECTROEROSIÓN

The objectives of this section are to provide a process that achieves the following objectives:

• Helps the functional requirements team formulate the project requirements

• Helps the system design team plan and implement an advanced secondary system that meets

those project requirements

For the functional requirements team, the process involves progressively figuring out (1) what people want the system to do, (2) what the consequent system requirements are, and (3) how to represent those requirements so that they can be easily and correctly interpreted by the system design team. In everything that follows this, the functional requirements team is engaged in specifying the criteria for successful design. This is the business described in Section 3.6.2 and

Project Management for Substation Automation

For the system design team, the process involves responding to the functional requirements in a way that achieves the desired results in the most advantageous way. This is where experience, common sense, good design practice, and familiarity with available products must come together to produce good decisions. Information and application aspects of the design process are

discussed in Sections 3.6.4 through 3.6.6.

3.6.1 Basic Concepts

This section provides a process for developing a project plan that really takes advantage of the new technologies to reinvent the substation. It does not define what the project objectives should be, but it will provide project teams with a plan for attaining their objectives. The following discussion overviews some basic concepts.

• Interoperability

The main goal of the IEC61850 communications standard is interoperability among smart devices and subsystems within a substation. This means that they have the capability to exchange and use information cooperatively, according to a planned system design. The way that they actually do this depends on the design goals selected by the functional requirements team and the design plans developed by the system design team.

When the project team understands the rudimentary concepts for applying these technologies, all they will need to get the job done is their utility knowledge, professional disciplines, imaginations, and common sense.

• The primary system

The traditional approach to substation design is naturally centered on the power system: buses, lines, transformers, LTCs, switches, breakers, capacitor banks, and reactors. This collective electrical infrastructure, which handles electrical power delivery, is called the primary system.

• The secondary system

The primary system is complemented by a secondary system, comprising all components and systems used to monitor, control, protect, and automate the substation. Because this

information infrastructure is critical to human safety, equipment safety, and system reliability, it has always been an essential part of substation planning and implementation. PTs, CTs, transducers, control panels, protection relays, RTUs, serial communications, and HMI are all examples of secondary systems.

In recent years, we have seen the emergence of intelligent devices (for example, IEDs), networked communications, programmable logic, and digital signal processing (DSP) capabilities for extracting a wealth of information from a simple 3-phase power connection. But to date, integration of the secondary system has been fragmented, composed of separate subsystems (for example, SCADA and protection) with little commonality.

IEC61850 now provides the means to integrate communications, information, and

applications into one coherent, flexible, very powerful framework for the secondary system. With its deployment, more information can be exchanged and more applications can run within the substation. We shall see that integrated, accessible information is truly the enabler

Project Management for Substation Automation

• The substation LAN

The IEC61850 standard enables information exchanges to be communicated over a

substation Ethernet network (the substation LAN) in a timely, secure, and flexible way. The LAN is connected to all IEC61850-savvy devices and subsystems in the substation.

Devices that do not have this capability are connected through a gateway, which must accommodate the communications limitations of such devices. Ideally, all communications among substation devices and subsystems is channeled through the substation LAN, eliminating the need for serial communication links and discrete field wiring, except where short, local interconnections are required (for example, within a breaker enclosure). This allows the secondary system to be implemented in a standardized way, independent of the specific information being exchanged and the specific applications being run. IEC61850 incorporates a variety of communication services and information models, the latter broadly representing data and functionality found in various pieces of substation equipment.

• Substation automation

Substation automation (SA) includes monitoring, control, protection, and automation applications. (Protection is really a of specialized automation application and, therefore, is identified separately.)

Those who use DNP or some other telecontrol protocol may wonder why the IEC61850 communications standard is necessary. The fact is that telecontrol protocols were strictly designed to support SCADA and nothing more. When demanding, higher performance applications are involved or when systems become complicated, telecontrol protocols do not provide the communication services required to support substation automation. IEC61850 also greatly simplifies system integration, data management, maintenance, and system validation.

• Distributed applications

We can even leverage this new technology to partition certain applications into cooperative modules, distributing them among different physical resources (for example, IEDs,

controllers, and other platforms). This provides unprecedented flexibility to manage the substation’s information and automation environment.

Protection relays provide a good example of how distributed applications work. Protective relays protect equipment in the substation (or connected to it) from scenarios that could cause damage or system instability. In recent years, many relay products have appeared with

programmable logic capabilities, allowing protection programs to be distributed across several relays, thus physically spanning areas of the facility that need to participate. But to date, interlocking status exchanged between relays continues to be signaled through point-to- point, hardwired contacts. IEC61850 networked communications, providing numerous virtual connections, can now be used to convey these interlocks. In like manner, all sorts of smart controllers, IEDs, and intelligent subsystems can cooperatively communicate peer-to- peer over the substation LAN to achieve very sophisticated capabilities.

Project Management for Substation Automation

3.6.2 Business Processes

To determine the functional requirements for the secondary system, we need to understand the business processes to be supported by the substation. This document defines business processes as activities that are deemed necessary for operational or administrative management of the power system. They may be mission-critical, mission-important, or mission-supportive. Business processes process may support the specific business responsibilities of a single department or they may provide a general benefit to several groups (for example, access to power system measurements and status). Business processes must comply with regulatory law and the utility’s corporate rules. They must also respect the utility’s corporate culture, as defined by current practice. Change leading to improvement is always desirable, but it needs to be coordinated among affected parties to produce acceptance and the anticipated benefits.

These business processes will determine the responsibilities and capabilities of the secondary system, which exists for no other purpose than to monitor, control, protect, and automate the substation in the manner that the utility wants it done.

The capture and documentation of business processes to be supported by the substation is the responsibility of the functional requirements team.

3.6.2.1 Describing a Business Process

A business process can technically be described as a sequence of actions and decisions designed to accomplish some tactical business goal. These actions and decisions may be performed by a combination of people, programs, and devices (actors). Decisions are made on the basis of observed conditions, constraints, and objectives. A business process is fully automated if it does not require any actions or decisions to be made by people. Some business processes may run continuously, while others run only under specified conditions. A flow diagram is one way to document a business process, but other tools are described in Section 5.

3.6.2.2 Principles for Documenting Business Processes

The following four principles are offered for documenting a business process:

1. Describe what the process must do or accomplish (that is, the requirements for fulfilling the