SINGLE PHASE MOBILE TRANSFORMER

The Single-Phase Transformers is an essential tool for experiments and demonstrations of transformer theory. It is made up of three identical transformers (except for the tertiary windings). Each transformer is inside a separate steel enclosure and all fit onto a frame which has small wheels for ease of mobility.

Each transformer has a selection of high-voltage (primary) and low-voltage (secondary) tappings to select a range of input and output voltages. They also have extra tertiary windings. The tertiary windings help compensate for any slight differences in the transformers when used in parallel. The transformers are separate units and will work as three individual single-phase transformers, or can connect to be a single three-phase transformer.

All tappings are accessible, so students may link the windings to suit any of the common single and threephase connections. All tappings connect to coloured, shrouded sockets for safety.

To show transformer principles clearly, the transformers operate as one volt each turn. This means that the no-load output voltage is the same as the number of turns on the secondary.

Thermocouples measure the temperatures of the primary windings, the secondary windings and the core of one of the transformers.

The thermocouples help to measure the temperature changes in a transformers. The readings help the student to understand the temperature specification for materials used in transformers. Note: you need a suitable K-type measuring instrument (not supplied) to measure the outputs of the thermocouples.
To allow a complete range of tests, IMPACT supply this product with three load banks; one resistive, one capacitive and one inductive (PSA50, PSA55 and PSA60).

SWITCHED BUSBAR MODULE

Part of the Modular Power Systems range, the Switched Busbar Module simulates industrial power line switching and monitoring.

Important note: This unit has no test circuit supplies or loads. To use it correctly, you must connect it to two or more units in the Modular Power System Laboratory range shown in the Available Experiments box below.

The fully instrumented unit includes two main control panels: the upper panel and the lower panel. Each panel has a detailed mimic diagram.

The lower panel has a double bus: a main bus and a standby bus or ‘reserve bus’. Each bus has two sections, split by circuit-breakers. Each bus includes individual bus section switches. Two bus-coupler switches connect the left and right-hand sections of the main bus and the standby bus.

The lower front panel also includes six feeders (three on each side of the bus). They are bi-directional, so the user can set them as incoming or outgoing (sink or source) feeders. The feeders connect to the other modules of the Power Systems range (supplies and loads). Each feeder also has its own circuit-breaker and meters to measure and display the current and voltage at each feeder. One feeder includes a ‘point-on-wave’ circuit-breaker. This allows the user to study the transients created when an alternating current is interrupted (switched).

The main bus, the standby bus and all feeders include current transformers (CTs). The user connects these to the protection relays to create ‘zone protection’ circuits and investigate faults applied to different parts of the double busbar system and the radial system. This is high-impedance differential protection.

The upper panel has a radial system of one incoming and three outgoing feeders. Each feeder includes a circuit-breaker, voltage and current meters, and current transformers for connection to the protection relay. The upper panel also includes test points for the double busbar and radial systems. These allow the user to connect faults or external loads (not supplied). The panel includes test/ fault switches, one with a digital timer. These allow the user to create open-circuit and short-circuit (line/line or line/earth) current faults and monitor their effects.

The user connects and sets the protection relays to detect line and earth currents, voltage and frequency faults. The relays also monitor and measure fault events and disturbances for fault analysis. The user sets the relays from their local control panel, or by a cable link to a suitable computer (computer not included) and software (included). When the user applies a circuit fault, the relays open circuit-breakers in the test circuits. The circuit-breakers also include hand-operated switches, and lamps. The lamps show whether the circuit-breakers are open or closed.

For more experiments in protection, the unit has an extra socket to connect an additional protection relay (not supplied).

Supplied with the equipment is a set of shrouded leads for the user to connect the test circuits together. The unit includes an emergency switch, a mains supply isolator and protection fuses.

The Modular Power System Laboratory allows experiments on power generation, transformation, transmission, distribution, utilisation and protection. Supplied with a comprehensive user guide which includes equipment descriptions, theory and experiments. Also, the open and flexible structure of the equipment makes it ideal for student projects and for lecturers to create their own experiments.

MODULAR POWER SYSTEM HUB

This unit is the ‘hub’ of the Modular Power System. It is needed to connect two or more of the modules together.

When connected to a suitable mains supply, the hub provides power for each part of the Modular Power System. It also links the electrical test circuits so students do not need to use long test leads between modules.

The hub links the emergency stop buttons of each connected module to give better safety in the laboratory.

The user can select from a choice of two emergency stop settings:

• One setting stops the power to only the affected module of the Modular Power System, leaving the others still powered.
• The other setting stops the power to all modules of the Modular Power System. The emergency stop setting switch is a keyswitch to prevent unauthorised use.

ELECTRICAL POWER SYSTEM SIMULATOR

Generator and grid supply

The PSS1 has a motor (prime mover) and generator set to simulate power generation. This set has characteristics similar to industrial turbine and generator sets for realistic experiments. The output of the generator passes through a generator transformer to a ‘generator bus’. Protection relays and circuit-breakers monitor and switch the generator field and output.

The PSS1 includes a fully monitored and protected grid supply transformer. This transformer simulates the larger grid transformers used in national grid supply systems. The grid transformer reduces the incoming mains supply to give the correct distribution voltage at the ‘grid bus’. It also allows students to correctly synchronise the generator output to the grid supply. For realistic tests, students can use the grid supply or the generator as a power source for their experiments.

Transmission lines

A set of reactances simulate transmission lines of different lengths to model the characteristics of overhead or underground power cables. Each line includes test points to monitor the conditions along the lines. The user can simulate faults at different places along the transmission lines and discover the effects. A dedicated distance protection relay protects the lines and can indicate how far along the line the fault has occurred.

Transformation, distribution and utilisation

As well as the grid supply and generator transformers, the Electrical Power System Simulator has two identical distribution transformers to simulate the distribution transformers fitted near to factories or houses. These transformers have variable tappings and feed a ‘utilisation bus’. Dedicated relays protect the transformers and can work in different ways, determined by student experiments. The utilisation bus simulates electrical consumers (houses and factories). It includes variable resistive, capacitive and inductive loads, with an induction motor (dynamic) load.

A switched busbar section includes a main bus and a standby or ‘reserve bus’. These simulate a real busswitching system in a power plant or power distribution station. Protection relays and circuit-breakers monitor and switch the incoming and outgoing feeders of the busbar. One feeder of the busbar has a ‘point-on-wave’ circuitbreaker for studies of switching transients.

Test points, transducers and fault switches

All the important circuits have test points connected to a set of test sockets. The students can link out these sockets or connect them to other test equipment. A set of transducers allows students to connect the test sockets to an oscilloscope (supplied) for transient measurements.

There are two fault switches to apply faults to different parts of the Power System Simulator. One fault switch is a standard three-phase switch; the other is a timed circuit breaker with a user-programmable digital timer to set a precise fault duration.

Protection relays, circuit breakers, blocking switches and instruments

All parts of the PSS1 include industrial-standard protection relays. The relays show students how actual power systems are protected and the different ways that they are protected. The students can set the relays from their control panels. The relays also include sockets to link them to a suitable computer for more detailed programming, if needed. The relays operate the circuit-breakers around the PSS1 for multiple experiments in protection. They also allow the user to try different methods of setting the operation of the relays, including:

• Auto-reclose
• Back tripping
• Directional tripping control
• Zone protection
• Protection grading

Blocking switches with warning lights allow the user to temporarily override the relay protection at key points, for enhanced experiments.

The circuit-breakers also include hand-operated switches, and lamps. The lamps show whether the circuit-breaker is open or closed.

Multi-function digital meters connect to all the important circuits to show the conditions of all three phases. A phase-angle meter shows the phase difference between any two voltages connected to it.

Moving coil meters show the prime mover voltage, current and power.

A self-contained motor and generator set that operates as a second generator for IMPACT’s Electrical Power System Simulator (PSS1). It provides extra experiments and studies into power generation.

The motor (prime mover) and generator set consists of two coupled machines mounted in the base of the control console. Manual or different types of automatic excitation control the output of the generator. A vector drive controls the speed of the motor. Digital meters show the conditions of the prime mover and generator.

The relays show students how actual generators are protected and the different ways that they are protected. Students can set the relays from their control panels. The relays also include sockets to link them to a suitable computer for more detailed programming, if needed. The relays operate the circuit-breakers around the second generator. The circuit-breakers also include hand-operated switches, and lamps. The lamps show whether the circuit-breaker is open or closed. The Second Generator links to the Power System Trainer at the higher voltage (transmission) level to simulate central generation, for example main power stations.

The Second Generator also links to the Electrical Power System Simulator at the lower voltage (utilisation) level to simulate embedded generation directly to a load, for example a generator at a factory or hospital.

Multifunction digital meters at the generator output and the utilisation and distribution outputs show the conditions of all three phases.