This trainer must have modular structure and it must consist of didactic panels that shall be installed on a vertical frame. 
The modularity of this didactic system must grant to the students a direct and  immediate approach to the topic, offering the opportunity to study various subjects performing different experiments:
Single-Phase Current Transformer
Single-Phase Ct At Overcurrent
Three-Phase Current Transformer
3–Phase Transformer Summing Circuit
Summation Current Transformer
Single-Phase Voltage Transformer
Three 1-Phase Voltage Transformers
Two 1-Pole Voltage Transformers
Under/Over Voltage Time Relay
Definite Time Overcurrent Relay
Inverse Time Overcurrent Relay
Earth-Fault Relay
Directional Earth-Fault Relay
Overcurrent And Earth-Fault Relay
The minimum set of power engineering modules should include the following:

THREE-PHASE POWER SUPPLY -

Didactic equipment: three-phase variable power supply, power supply unit for variable 3-phase voltage suitable for supplying ac machines. It must provide an AC output 3-phase from 0 to 380 V, 8 A minimum. 
It must be provided with a 16 A, 30 mA differential magneto-thermal main switch, a key operated
emergency push-button, start and stop push-buttons, a motor protection circuit breaker: 6.3 to 10 A, a digital ammeter and a digital switchable voltmeter. 4 mm safety terminals for electrical connections included. 
The output voltage must be set by a rotary knob with 0-100% scale. 
Supply voltage:three-phase from mains.

RESISTIVE LOAD

didactic equipment:It must consist in a single or three-phase resistive step-variable load. Housed in a metallic box.

MECHANICAL FEATURES
The load shall be composed of a rugged metal structure and of a front metal panel.
On the front panel all the controls, the protection, the output terminals and a clear synoptic diagram, shall be collected.

ELECTRIC FEATURES
The load shall be composed of resistances, with possibility of star, delta and parallel connection, controlled by three switches. This item must be provided also with fuses protection.
As a function of the switch positions, there shall be the following phase values:
Position    Resistance      Max power per phase
1    1050 Ohm           46 W
2    750 Ohm            65 W
3    435 Ohm           110 W
4    300 Ohm        160 W
5    213 Ohm        230 W
6    150 Ohm        330 W
7    123 Ohm        400 W
Maximum power in single or three phase connection must be 1200 W.
Rated voltage in star connection must be 380 V, in D connection must be 220V, in single-phase must be 220V. 4 mm. safety terminal included on the front panel for the electrical connection.

EXPERIMENT TRANSFORMER -

Didactic equipment   
With rotary knob to supply a set of single-phase voltages. It must also be possible to tap off three single-phase floating voltages by means of an isolating transformer.
 It must be provided with bridge rectifier for dc voltage output. With the minimum outputs: 0... 250 V / 3 A, 0 ... 42 V / 3 A, 0 ... 24 V / 6 A or 0 ... 12 V / 12 A (floating values), dc voltage: 25 A, bridge rectifier for all ranges, Output protection: 2 magneto-thermal circuit breakers, 3.5 A and 0.8 A ;  4 mm safety terminals for the electrical connection must be included.

THREE-PHASE TRANSFORMER –

• didactic equipment
• Three-phase transformer for feeding a transmission  line model 380 kV with scale factor 1:1000 Primary
•  3 x 380 V windings with tap at 220 V    
•  Star or delta connection Secondary
•  3 x 220 V windings with taps at +5%,-5%,-10%,-15%
•  Star connection for 3 x 380 V
•  Various star connections possible
•  Rated power: 800 VA

POWER CIRCUIT BREAKER -

Didactic equipment: Three-phase power circuit breaker with normally closed auxiliary contact.

Features:

• Contact load capability: 400 Vac, 3 A
• Supply voltage: single-phase from mains
• Power circuit:
• Insulation voltage: 750V
• Thermal current : 20A
• Auxiliary contact:
• Insulation voltage: 750V.
• Rated current: 3A
• Auxiliary power:
• Single-phase voltage 220V, 50-60Hz
• It must be possible to control manually the power breaker switch using the push-buttons “on”and
• “off” or externally via the switching contact PLC or RELAY.
• This power contacts state shall be indicated by leds:
• Green led = open contacts.
• Red led = closed contacts.
• While at SIGNAL OUTPUT terminals will be  available a TTL level:
• Low level ( 0V )= open contacts.
• High level ( 5V )= closed contacts.
• The RS flip-flop state shall be indicated by a led:
• Yellow led = set flip-flop.
• 4 mm. safety terminal and 2 mm. terminals included on the front panel for the electrical connection.
• It must be supplied with manual in English language
• CT LOAD - Didactic equipment: module with insulated panel, single-phase current load transformer consisting of two separated ohmic resistors: 
• Fixed resistor: 0.5 Q, load 7 A 
• Variable resistor: 0 ... 60 Q, load 1 A 
• Range: 0 ... 100%    
• 4 mm. safety terminals included on the front panel for the electrical connection.
• VT LOAD -Didactic equipment: module with
• insulated panel, single-phase voltage load transformer consisting of two separated ohmic resistors: 
• Fixed resistor: 220 Q, load 0.5 A 
• Variable resistor: 330 ... 1930 Q,
• 4 mm. safety terminals included on the front panel for the electrical connection.

UNDER/OVER VOLTAGE TIME RELAY

•  Didactic equipment: module with insulated panel, under/over voltage time relay, relay for monitoring the over-voltage and the under-voltage in an alternating three-phase mains. Max adjustable set point: 0/+20% of the rated voltage. Min adjustable set point: 0/+20% of the rated voltage. 
• Adjustable delay timer activated when the max. set point is exceeded. 
• Adjustable delay timer activated when the min. set point is exceeded.
• It must be possible to connect the three-phase line 3x380V to the terminals.
• One output relay with two change over contacts: (5A – 230Vac) with resistive load.
• NC contacts: device not supplied or in alarm
• Self-supplied by the voltage to be monitored: (380 ÷ 418)
• 4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.

INVERSE TIME OVERCURRENT RELAY -

Didactic equipment:  module with insulated panel, inverse time over-current relay, three-phase over current and earth fault relay with programmable time- current curves suitable for protection of power distribution systems with insulated, resistance earthed or compensated neutral. 
Rated input current selectable 1A or 5A, 50/60 Hz. It must be provided with three independent over current elements, three earth fault elements, a thermal image element, a blocking output and blocking input for pilot wire selectivity coordination, a breaker failure protection, a time tagged multiple event recording, an oscillographic wave form capture, Modbus RTU / IEC870-5-103 communication, Protocols, display LCD 16 (2x8) characters.
4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.

DEFINITE TIME OVER CURRENT RELAY -

Didactic equipment:  module with insulated panel, definite time over-current relay, relay for monitoring the current of a three-phase load (typically a motor) and performing a protection with alarm. Max. adjustable set point, divided in 10 parts.Adjustable timer (0.1 ... 30 s). 
The delay time must start as soon as the current exceeds the max set point. Adjustable initial timer (0.1 ... 30 s). 
The timer must activate when the current exceeds 5% of the max range. Current range: 0.25 ... 5 A with direct insertion
(galvanic isolation). For currents higher than 5 A an external CT.../5 A must be used). One changeover contact: 5 A /
230 Vac with resistive load. NC contacts: device not supplied or in alarm. Supply voltage: single-phase from main. 4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.

COMBINED OVERCURRENT AND EARTH FAULT RELAY -

Didactic equipment:  module with insulated panel, combined over-current & earth fault relay with programmable time-current curves suitable for protection of power distribution systems with insulated, resistance earthed or compensated neutral. 
It must be provided with three phase-fault elements, three earth fault elements, time current curves selectable according to IEC/IEEE standards, a breaker failure protection, a trip circuit breaker control via serial port, a blocking output and blocking input for pilot wire selectivity coordination, a time tagged multiple event recording, oscillographic wave form capture, modbus RTU / IEC870-5-103 communication Protocols, display LCD 16 (2x8) characters, optional expansion input/output modules, rated input current selectable 1A or 5A, 50/60 Hz. 3rd harmonic filter on the neutral input current. .
4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.

SINGLE-PHASE DIRECTIONAL RELAY

- Didactic equipment:  module with insulated panel, directional relay, multifunction relay suitable for protection of HV, MV, LV power transmission and distribution systems. Accidental earth-fault directional relay for selective protection of the power supply in isolated neutral and earthed networks. It must be complete with Data Logger system. It must be provided with three independent over current elements, two different thresholds for directional and non directional current with selectable trip, standard IEC Protection against switch opening failure, block input and output, time tagged multiple event recording, oscillographic wave form capture, Modbus RTU / IEC870-5-103, display LCD 16 (2x8) characters, switch control through serial port, communication protocol, 3rd Harmonic Filter on the neutral input current. 4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.
L/C LOADS - Didactic equipment: module with insulated panel, L/C loads, inductive and capacitive loads suitable for simulating various fault types, in order to trigger the single-phase directional relay. Inductance: 0.1 / 0.2 / 0.3 / 0.4 H. Rated voltage: 220 V, 50 Hz. 
Rated current: 0.5 A.
Capacitance: 2 / 4 / 8 / 16 uF. 
Rated voltage: 450 Vac
4 mm. safety terminals included on the front panel for the electrical connection.

EARTH FAULT WARNING RELAY -

Didactic equipment: module with insulated panel, Multifunction three phase overvoltage/ undervoltage relay. Three-phase voltage relay, suitable for protection of HV, MV, LV power transmission and distribution systems. The relay must measure the true R.M.S. value of the 3 phase to neutral voltages fed to three transformers. It must be provided with two under voltage elements, two over voltage elements, one under frequency element, one over frequency element, one omopolar sequence over voltage element, one negative sequence over voltage element, one positive sequence under voltage element, time tagged multiple event recording, oscillographic wave form capture, Modbus RTU / IEC870-5-103, Display LCD 16 (2x8)
characters, communication Protocol. 4 mm. safety terminals and 2 mm. terminals included on the front panel for the electrical connection.

THREE-PHASE SUPPLY UNIT -

Didactic equipment: Power supply unit for three-phase  connection with 4-pole cam mains switch. 
25 A current operated earth leakage circuit breaker, sensitivity 30 mA.
Triple-pole motor protection switch: 6.3 to 10 A.
Three-phase indicator lamps.
Output through 5 safety terminals: L1, L2, L3, N and PE.
Switch for simulation of wind or  photovoltaic energy power source
4 mm. safety terminal included on the front panel for the electrical connection.

MOVING COIL AMMETER MODULE -

• didactic equipment    4 pcs                                                         
• The module must consist of a magneto-electric meter for ac and dc measurements.
• Scale: 50 divisions - the scale shall made open and reasonably uniform down to about 20 percent of the full-scale reading.
• Range: 100, 500 and 1000 mA, ac/dc
• Accuracy class: 1.5
• This module must have insulated front panel , 4 mm safety terminals, one selector and one analog meter.
• The module must be supplied with manual in English language.

SINGLE-PHASE CURRENT TRANSFORMER -

Didactic equipment: module with insulated panel, single-phase current transformer with primary 5/1A and secondary 1A, accuracy class: 1. 4 mm safety terminals for electrical connections included.

THREE-PHASE CURRENT TRANSFORMER -

Didactic equipments: module with insulated panel, three-phase current transformer with primary 5/1A and secondary 1A, accuracy class: 1. 4 mm safety terminals for electrical connections included.

SINGLE -PHASE VOLTAGE TRANSFORMER

 Didactic equipment: module with insulated panel, single-phase voltage transformer with primary 380V/V3 (220V) and secondary 100 V/V3, accuracy class: 1. 4 mm safety terminals for electrical connections included.

THREE-PHASE VOLTAGE TRANSFORMER -

Didactic equipment: module with insulated panel, three-phase voltage transformer with primary 380V/V3 (220V) and secondary 100 V/V3, accuracy class: 1. 4 mm safety terminals for electrical connections included.

SUMMATION CURRENT TRANSFORMER

Didactic equipment: module with insulated panel, summation current transformer with primary current 5 x 2.5 A and secondary current 1A, accuracy class: 1. 4 mm safety terminals for electrical connections included.

MOVING COIL AMMETER MODULE

• didactic equipment 
• This module must be suitable for ac and dc current measurements.

Technical features:

• Scale: 50 divisions - the scale shall made open and reasonably uniform down to about 20 percent of the full-scale reading.
• Range: 2.5 A - 1.25 A
• Accuracy class: 1.5
• AC/DC measurements
• This module must have insulated front panel, 4 mm. safety terminals, one selector and one analog meter.
• The module must be supplied with manual in English language.

MOVING IRON VOLTMETER MODULE

• didactic equipment    4 pcs  
• This module must be suitable for ac and dc voltage measurements.

Technical features:

• Scale: 50 divisions - the scale shall be made open and reasonably uniform down to about 20% of the full-scale reading.
• Range: 125-250-500 V
• Range changeover switch
• Accuracy class: 1.5
• This module must have insulated front panel with the electrical scheme, 4 mm safety terminals, fuse protection and one analog meter. One selector shall be included in this panel.
• The module must be supplied with manual in English language.

MOVING IRON AMMETER MODULE -

• didactic equipment   2 pcs   
• Electromagnetic
• meter for AC and DC measurement
• Scale: 50 divisions.
• The scale shall be made open and reasonably uniform down to about 20% of the
• full-scale reading.
• Range: 5A.
• Accuracy class: 1.5 
• The meter must be connected in series and carries the circuit current      
• This module must have insulated front panel,4 mm  safety terminals and one analog meter.
• The module must be supplied with manual in English language.
• Electronic stopclock with LCD display
• Acoustic Continuity tester upto 1 kQ

WORKBENCH 

1. This item must consist in a large sized bilaminated wooden board and square legs with compensation feet.
2. Dimensions: 2 x 0,8 x 0,9 m
3. A set of cables with at least 80 connecting leads with security plugs of different colours, length and sections.

THREE-LEVEL FRAME

•  2 pcs
• Metal frame with three levels for fitting the modules of the laboratory 
• Set 7