Fiber Optic Communications for Utility Systems

An integrated T1/E1 multiplexer providing complete substation, telephone and system protection communications

In today's information intensive world, Utility Relay and Communication Engineers need access to the increased data available from modern protective relays, RTUs and other substation equipment. The need to integrate and reliably communicate this information efficiently between locations is becoming increasingly important. Pulsar Technologies Inc. offers FOCUS, designed specifically for the increasing needs of the power industry.

FOCUS provides a flexible package for multiplexing virtually any type of signal or data directly onto fiber optic cables. Electrical interfaces to higher order multiplexing schemes such as M13, SDH or SONET (OC-3, OC-12, etc.) are also available. FOCUS drop and insert networks will work effectively with any combination of mixed communication links such as 1300/1550 nm single-mode fiber optics, SDH, SONET and digital microwave. This allows easy integration into existing systems. The drop and insert feature also improves channel conservation and eliminates the need for back-to-back channel banks. FOCUS offers four T1/E1 ports in one chassis, which can be fiber optic, electrical or a combination of both. Both features enhance the application of FOCUS for looped networks and loops with spurs.

FOCUS uses byte-interleaved time division multiplexing at a standard T1/E1, 1.544/2.048 Mbps rate, in ESF/HDB3 format; this assures compatibility with standard communications networks and DS1/DS0 test equipment. The FOCUS T1/E1 system can multiplex up to 24/30 channels into its data stream. Each of these channels may be used for transmission of analog or digital data, pilot wire differential data, or other relay information required by POTT, PUTT, blocking, unblocking or DITT systems.

Increasing demand for real time information from the substation has created a need for "intelligent" communication systems that facilitate setup, modification and data acquisition. The FOCUS system is designed to meet these demands by being 100% software configurable without the use of DIP switches or jumpers.

The PC-based FOCUS Configuration Software (FCS) supplied with every system provides a Windows® interface for all system and channel settings. Some of these include time-slot mapping, local and remote loopbacks, system status, alarms, targets, data stream errors and channel module settings including trip delays, signal gain, security levels. The optical Remote Node Configuration (RNC) package enables execution of all FCS commands over the FOCUS network to all remote terminals. Remote communication is as simple as connecting a PC to any FOCUS node and selecting the desired remote node from a "pull-down" menu.

Once communication is established, commands are executed as if the user were standing in front of the remote chassis. RNC saves valuable time and money since all modifications and data collection can be accomplished without having to visit every substation individually.

FOCUS offers several network management options for the protection of critical communication channels in the event of a link or node failure. The four-fiber hot-standby ring option utilizes two pairs of fibers between adjacent nodes in the ring. One of the fiber pairs is used as the main communication path, and the other pair is used as a hot standby or redundant path which is shared by all nodes in the loop. A break in the primary path between two nodes initiates rerouting of all 24/30 channels through the standby fibers. The rerouted signal travels in the opposite direction around the ring to arrive at the node on the opposite side of the break. This procedure reliably reconnects all channels affected by the break.

The signals are automatically returned to the main fibers when the normal path has been restored. Unlike traditional path-switched schemes, the four-fiber hot-standby ring allows the user to make use of the full T1/E1 bandwidth between each adjacent station. (All 24/30 time slots between any two locations can be reused any number of times around the loop.)

The system provides fast hardware-based service restoration with complete reconfiguration typically in less than 1ms. High reliability is maintained by continuous monitoring of the standby fibers to insure availability in the event of a fiber link or node failure.

The Alternate Path Mode (APM) software allows for any channel module, in a loop configuration network, to link to its complement should the primary path become non-functional. All required rerouting is performed automatically without any user intervention or initial setup for designating rerouted channels.

All 24/30 channels in the T1/E1 stream are available to the user and may be used only once within the loop. When a link or node fails, adjacent nodes detect the failure and send a message in the opposite direction around the ring. The message specifies which channels have been affected by the failure.

Each node containing an affected channel drop reverses the transmit direction for that channel. Nodes located between the affected channel drop nodes are converted to pass-throughs for these channels. This flip-flop procedure quickly reconnects all broken channels in the opposite direction around the loop. When the primary path is re-established, a complementary message is sent causing each node to return to its original setting.

FIBER OPTIC COMMUNICATIONS FOR UTILITY SYSTEMS

Channel Interfaces

Two-wire Voice (V2T, V2W)

The V2W and V2T modules provide two-wire voice and modem communication between two locations. Both modules support two channels which are configured independently. They are supplied with RJ-9 jacks and compression-type terminal blocks for connecting telephones or modems. Applications for these modules include ringdown circuits or remote telephone extensions.

Four-wire Voice (V4W)

The V4W module allows for the transmission of audio tones and data, as well as E&M signaling information. Two independent channels are provided on each module. Applications include traditional audio tones for relaying, telemetry or any device that uses a four-wire modem to transmit data (e.g. SCADA RTU)

Protective Relay Interface (PRI, PRS)

The Protective Relay Interface provides four independent programmable bi-directional transfer trip circuits with either solid-state or mechanical contact outputs. These optically-isolated trip circuits are encoded, allowing each one to operate independently without affecting the dependability, security or response time of the remaining circuits. Guard and alarm output contact are also provided on the module. Applications include DTT, PUTT, POTT, Directional Comparison Blocking and Unblocking.

Contact Transfer (CTR)

The Contact Transfer module provides eight independent bi-directional contact closure circuits. It can take in up to eight contacts and transfer their status to the remote end CTR module. This is ideal for extending the reach of a SCADA RTU for remote alarm indications.

Low-Speed Data (232)

This module provides two independent RS-232 data circuits over which the user can transparently transmit and receive data and modem control signals at speeds up to 19.2Kbps asynchronous. No presetting of data rate is required. The module supports CTS, RTS, DTR and DSR handshake lines.

Current Differential (HCB, SPD)

The current differential module connects directly to HCB, HCB-1 or SPD relays. It monitors the voltage and current of the connected pilot wire locally and transmits this data to the remote relay. Using this module via the FOCUS system eliminates the need for metallic pilot wire, insulating transformers, neutralizing reactors, drainage reactors and gas tubes. It also replaces pilot wire monitoring equipment and the dc auxiliary transfer trip function.

The high-speed data module communicates with EIA R-S530/422 (64R), CCITT V.35 (64V), G703.2 (64G) or RS422 fiber link to FOCUS (64F) data terminals running at 56 or 64 Kbps synchronous.

The PLD module provides multi-drop RS-232 data communication to several sites over a single DS0 channel. The PLD can be configured to operate in either internal or external mode. In internal mode, communications between a computer at the head card and an RS-232 device at the selected remote site is possible. This allows access to LANs in several substations from one location. External addressing mode is used with a SCADA master computer at the head PLD sending messages through all PLDs to their connected RTUs. The RTU , detecting its own address, temporarily takes control of the transmit path back to the SCADA master computer.

Voice (V2W, V2T, V4W)

Application

Low Speed Data (232)

Application

High Speed Data (64R, 64V, 64G, 64F)

Application

Protective Relay Interface (PRI, PRS)

Application

Pilot Wire Interface (HCB, SPD)

Application

Contact Transfer Module (CTR)

Application

Party Line Data (PLD)

Application

System Applications

FOCUS is ideally suited for various SCADA/RTU applications where a collection of analog and digital signals must be transferred from one location to another. One example is a remote substation transmitting SCADA information to a location with ties to the SCADA network. The Link between these terminals uses just one pair of fiber optic cables in place of the multitude of cabling normally required. Similar applications within power plants and industrial facilities are also common examples.

Using the Party Line Data module (PLD), a system of polled RTUs can be used in a multi-drop RS-232 network utilizing just one DS0 channel. The PLD can also be used to access non-addressable RS-232 devices individually or as part of a substation LAN.

The FOCUS pilot wire differential relay interface enhances communications reliability between HCB, HCB-1 and SPD relays. The interface is designed so that no modifications to the protective relays are required. The direct transfer trip capability normally offered within the pilot wire monitoring relays is also included.

Protective relay interface modules are used to replace the conventional audio tone or power-line carrier channel equipment used in POTT, PUTT, DTT, unblocking, or blocking relay systems. Logic to interface with virtually any protective relay scheme is included with the programmable levels of dependability and security.

Architecture

The FOCUS hardware and software were carefully designed to operate within the harsh environment of the substation. All external interfaces exceed applicable ANSI, IEEE and IEC standards for fast transient, surge withstand capability, and EMI/RFI immunity. The compact modular design of FOCUS permits easy installation within existing panels, while maintaining the flexibility to grow as your system needs change.

Interface modules for a variety of communication needs may plug into any of 12 position-independent module slots in the chassis. One 19" wide, 3 R.U. high, chassis provides ample space for most substation channel requirements.

If only voice and/or data channels are used, 24 channels will fit into the main chassis. For communication-intensive substations requiring a large number of channels other than voice or data, an additional 3 R.U. expansion chassis can be added.

From a simple point-to-point linear application to a full-featured drop and insert looped network, the FOCUS architecture permits you to design a compact, cost-effective, reliable communication system which is ideal for most applications. Unlike traditional channel banks, FOCUS offers up to four T-1 ports in a single chassis under the control of a single integrated cross-connect switch.

Reliability and Availability

FOCUS maintains high reliability through the use of large scale integration and multiple copies of the system data in memory. Channel cards may be inserted or removed without powering down the chassis. An optional redundant power supply is also available. The microprocessor based maintenance module designates all channel time slots and provides self diagnostics for quick and easy fault isolation. Using the supplied FCS software, FOCUS is completely configurable from local or remote locations.

The maintenance module may include an optional party line order wire (PLOW) service voice channel, separate from the channel cards, to assist in system setup. Major and minor alarms are available locally in the form of LEDs, relay contacts and an RS-232 interface for computer access.