A METHOD AND AN APPARATUS FOR SINGLE PHASE LOAD SWITCHING
FIELD OF THE INVENTION
[0001] The present invention relates in general to systems and methods of
simulating field like conditions in a laboratory and, more particularly to a novel system and method to create the field conditions like voltage failure, voltage fluctuation/switching at fast rate, load changeover, load switching at fast rate in a laboratory to understand its effect on electrical equipments like meters and to understand the behavior of meters in these field conditions.
BACKGROUND OF THE INVENTION
[0002] In electrical distribution systems the equipments used, are subjected to
various electrical loads of varying magnitude, fluctuations and their combinations which do not follow a regular pattern. In order to improve the design and to study the effects of different conditions on electrical equipments, it is often necessary to create field conditions like voltage failure, voltage fluctuation/switching at fast rate, load changeover, load switching at fast rate in a laboratory.
[0003] In order to test electrical equipment in a laboratory it is necessary to load
the equipment with the loads similar to field conditions to study their effect on the working of the equipment.
[0004] Traditionally several systems and methods to simulate the field conditions
in a laboratory exists. They include different loads viz. resistive, capacitive and inductive controlled by analog times to select timing of these loads which creates few conditions in the laboratory. But they have to be operated manually and only switches the loads ON/OFF and specifies the time for which a particular load in ON/OFF. Also it does not allow creating a fluctuating load condition.
[0005] Thus there exists a need of a system and method which overcomes above
mentioned drawbacks of a analog timer and gives the user more flexibility to create various field like conditions.

SUMMARY OF THE INVENTION
[0006] The present invention relates to a novel system and method to create field
conditions in a laboratory for testing electrical equipments. The apparatus according to an embodiment of the present invention comprises a power supply means, a means to receive user input, a micro-controller to process the user input, memory to store the user input and status of the apparatus, a firmware for receiving the user input from the microcontroller and creating the field conditions, and a display means for displaying the user input and the status of the apparatus. The apparatus allows programming the user input. The method for simulating field conditions in a laboratory for testing electrical equipment, comprises the steps of receiving user input, where the user input includes magnitude of different loads, load switching time, load overlap time, load fluctuation intervals and counts, validating the user input data in a micro-controller, such that the user inputs complies with the acceptable limits of the method, supplying the user input after validating to a firmware to generate the field conditions and applying the field conditions on the electrical equipment used for testing.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a schematic diagram of the apparatus for simulating field
conditions in a laboratory according to an embodiment of the present invention.
[0008] FIG. 2 shows the technical details of the power supply means according to
an embodiment of the present invention.
[0009] FIG. 3 is a circuit diagram of the apparatus according to an embodiment of
the present invention.
[0010] FIG. 4 is a schematic diagram of the method for simulating field
conditions in a laboratory according to an embodiment of the present invention.
[0011] FIG. 5 is a flowchart of the user input according to an embodiment of the
present invention.

DETAILED DESCRIPTION OF THE INVENTION
[0012] Referring to FIG 1, an overview of an apparatus 10 for simulating field
conditions in a laboratory for testing electrical equipment 12 is shown. The apparatus 10 comprises a power supply means 14 to the apparatus, a means 16 to receive user input 18, a micro-controller 20 to process the user input 18, memory 22 to store the user input 18 and status of the apparatus 10, a firmware 24 for receiving the user input 18 from the micro-controller 20 and creating the field conditions and a display means 26 for showing the user input 18 and the status of the apparatus 10.
[0013] The field conditions include voltage failure, voltage fluctuation/ switching
at fast rate, load changeover, load switching at fast rate. These field conditions are generated by using the apparatus 10.
[0014] FIG. 2 shows the technical details of the power supply means 14 used in a
preferred embodiment of the present invention. The power supply means 14 includes a 240V A-C supply, a transformer, a rectifier/ filter and regulator and is adapted to supply a DC output of 5V and 24 V. The power supply is based on the transformer and it is a linear power supply.
[0015] In a further preferred embodiment of the present invention the means 16 to
receive user input include four keys to enter the user input 18. It also includes a power ON/Off switch to start the apparatus 10.
[0016] In a further preferred embodiment of the present invention the micro-
controller 20 is adapted to be programmed as per the requirements of the user. A Programmable Interface Controller PIC 16F877A and IC ULN2803/2804 is used as the micro-controller 20.
[0017] The memory 22 to store the user input 18 and status of the apparatus is
adapted to restart the apparatus 10 from the same condition where it got interrupted due to accidental power failure. It is the internal EEPROM ( Electrically Erasible Programmable Read Only Memory) of the PIC 16F877A.
[0018] The firmware 24 includes one resistor, one capacitor and one inductor to
generate namely resistance, capacitance and inductance loads and are capable of acting indpendently or in combination with one another. They are also capable of producing

varying loads, fluctuations over a period of pre-specified time intervals independently
and in combinations. Relays are used to switch loads or currents.
[0019] The display means 26 is a LCD 16x2 and it shows the user input, the loads
of the firmware and the status of the apparatus 10 at any given time.
[0020] FIG. 3 is a circuit diagram of the apparatus 10 according to a preferred
embodiment of the present invention. The diagram shows the electrical connections
between the power supply means 14, the micro-controller 20 PIC16F877A, memory 22
ULN2804, display means 26 LCD 16x2 and other devices used.
[0021] Referring to FIG 4, the method 100 for simulating field conditions in a
laboratory for testing electrical equipment 11 starts with the step 102 of receiving the user
input 18, which includes magnitude of different loads, load switching time, load overlap
time, load fluctuation intervals and counts.
[0022] The user input includes Load ON Time, Load Overlap Time, Chattering/
Fluctuating Count and Chattering Interval. The Load ON Time is the time for which a
particular load (resistive, capacitive or inductive) is active. Load Overlap Time is the
time for which more than one loads are active simultaneously. Chattering/ Fluctuating
Count is the number of times a load fluctuates and Chattering Interval is the time for
which the load is fluctuating.
[0023] Following are the limits of all these user inputs according to a preferred
embodiment of the present invention:
- Load ON Time: 1 minute to 60 minutes
- Load Overlap Time: 1 minute to 60minutes.
- Chattering count: 1 to 20 count
- Chattering interval: 20 milli-seconds to 50 milli-seconds
[0024] In next step 104 the user input 18 data is validated in the micro-controller
20, such that the user input 18 is within the acceptable safe limit of the method 100 and thereby maintains safety of the apparatus 10. If the user input 180 does comply with the method limits then the control goes to step 106 which provides a default user input to be used for next steps and if the user input is within safe limits then the control goes to step 108.

[0025] In step 108 the user input after validation is supplied to the firmware 24 to
generate the field conditions.
[0026] In next step 110 the firmware 24 applies the field conditions on the
electrical equipment 12 used for testing.
[0027] Referring to FIG. 5 a flowchart of the user input 18 according to an
embodiment of the present invention is shown. First the power is switched ON which
also starts the booting of the micro-controller 20. Now when UP key is pressed it gives an
option to go to Programming mode or to erase the (EEPROM). If erase memory is
selected then after erasing the control goes to the Programming mode again.
[0028] From Programming mode the user can press 'L' key to read the memory
and validate the data in the memory. After validating the memory data the task execution
is done based on user input data, if the data is within safe limits otherwise the default task
execution is done.
[0029] From the Programming mode if 'R' key is pressed, it gives the choice of
using standard profiles of pre-specified sequences or to enter parameters for customized
programming. Based on this selection the task execution is done.
[0030] The sequences of user inputs are as shown below:
1. Test Sequences:
Following are the inputs from user:
• Chattering count: Limit is 1 to 20 count
• Chattering interval: Limit is 20 milli-seconds to 50 milli-seconds
• Load ON Time : Limit is 1 minute to 60 minutes
• Load Overlap Time: Limit is lminute to 60 minutes.
For Sequence 1 and Sequence 2, above user inputs are being used.
For Sequence 1, all above user inputs are being used.
For Sequence 2, Load ON Time and Load OFF Time is being used.
Here Contactor 1 = Resistive Load,
Contactor-2 = Capacitive Load, and Contactor-3 = Inductive Load
Sequence-1:
• Contactor-l=ON , Contactor-2=OFF , Contactor-3=OFF
• Contactor-l=ON, Contactor-2=ON, Contactor-3 =OFF
• Contactor-l=ON, Contactor-2=OFF, Contactor-3=Chattering

• Contactor-1=0N, Contactor-2=OFF , Contactor-3=ON
• Contactor- l=ON , Contactor-2=ON , Contactor-3=ON
• Contactor-l=Chattering, Contactor-2=OFF , Contactor-3=OFF
• Contactor-l=Chattering,Contactor-2=ON,Contactor-3=OFF
• Contactor- 1=0N, Contactor-2=OFF , Contactor-3=OFF
• Contactor-1 =OFF, Contactor-2=OFF, Contactor-3=OFF
Sequence-2:
• Contactor-l=ON, Contactor-2=ON , Contactor-3=OFF
• Contactor- l=ON , Contactor-2=OFF , Contactor-3=ON
• Contactor-1 =ON, Contactor-2=ON , Contactor-3=ON
• Contactor-l=OFF , Contactor-2=OFF, Contactor-3=OFF
Default setting (Here ON Time is fixed i.e. 1 minute)
• Contactor-l=ON , Contactor-2=ON , Contactor-3=OFF
• Contactor- l=ON, Contactor-2=OFF , Contactor-3=ON
• Contactor-l=ON, Contactor-2=ON, Contactor-3=ON
• Contactor-lOFF, Contactor-2=OFF , Contactor-3=OFF
[0031] The apparatus can be programmed as many times as needed by using the
above sequences and by making customized sequences. The IDE used is MPLAB Ver7.50 and C Compiler used is Hi-tech PICC Ver 8.02PL1 in a preferred embodiment of the present invention.

We Claim:
1. An apparatus for simulating field conditions in a laboratory for testing electrical
equipment, comprising:
- a power supply means to the apparatus;
- a means to receive user input;
- a micro-controller to process the user input;
- memory to store the user input and status of the apparatus;
- a firmware for receiving the user input from the micro-controller and creating the field conditions, comprising:

- at least one resistor to create resistive load;
- at least one capacitor to create capacitive load; and
- at least one inductor to create inductive load; and
- a display means for showing the user input and the status of the apparatus.
2. The apparatus according to claim 1, wherein the field conditions include voltage failure, voltage fluctuation, voltage switching at fast rate, load changeover, load switching at fast rate.
3. The apparatus according to any of the preceding cliams, wherein the means to receive user input include keys to enter the input and start the apparatus.
4. The apparatus according to any of the preceding cliams, wherein the micro-controller is adapted to program the user input.
5. The apparatus according to any of the preceding cliams, wherein the memory to store the user input and status of the apparatus is adapted to restart the apparatus from the same condition where it got interrupted due to accidental power failure.
6. The apparatus according to any of the preceding cliams, wherein the at least one resistor, at least one capacitor and at least one inductor are capable of producing varying

loads, fluctuations over a period of pre-specified time intervals independently and in combinations thereof.
7. A method for simulating field conditions in a laboratory for testing electrical
equipment, comprising the steps of:
- receiving user input, wherein the user input includes magnitude of differerent loads,
load switching time, load overlap time, load fluctuation intervals and counts;
- validating the user input data in a micro-controller, such that the user inputs complies
with the acceptable limits of the method;
- supplying the user input after validating to a firmware, comprising at least one resistor,
at least one capacitor and at least one inductor to generate the field conditions; and
- applying the field conditions on the electrical equipment used for testing.
8. The method according to claim 7, wherein the user input is programmed as per the
field conditions required to be simulated.
9. The method according to claims 7-8, wherein the micro-controller is capable of
supplying a default pre-specified user input to the firmware in case the user inputs does
not comply with the limits of the method or accidental interruption of the method before
completion.