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Tripping means the interruption in electricity supply. An electric line is tripped if it starts carrying the fault current or it gets broken or due to several other reasons. It is a protective measure that essentially isolates the faulty lines from the rest of the healthy sections. So basically cascade tripping is tripping of protective devices to isolate the part or parts of the system to avoid the damage to the load and the system equipment. Sometimes tripping of power grid takes place due to unbalanced conditions is also called as cascade tripping.
Modern power systems experience many disturbances and the majority of them are eliminated by relay protection and emergency control system. According to historical data , relay miss-operation is one of the contributing factor of 70% of major disturbances in the power system. With rapid growth of loads , transmission distances , HVDC and FACTs devices , the dynamic behaviors of the power system are getting more and more complicated. A single fault is unlikely to destroy a modern power system , but information deficiency , hidden failures of relays, faults of other secondary system or human errors may be the cause of cascading events and the system, however strong may evolve in to power calamity.
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Cascading outages may happen in AC lines, DC lines, AC-DC line, sending area and receiving area as well.
When the load demand is larger than the power generated the frequency of the machine goes down. When the value of his frequency lowers than the nominal value of the frequency the grid trips and the loss of power occurs.
These power failures are not normal, they sometimes lead to blackout conditions if there is no backup protection available.
In the power grid when one of the components fails and then its load is shifted to the nearby system. Those nearby systems may push to work beyond their capacity so they get overload and shift their load to another system. Cascade failure was mainly seen in high voltage systems where a single paint failure on a completely loaded or somewhat overloaded system results into surges of spikes across the system.
Once power is generated it has to be supplied to somewhere else. If it is then the load demand it will cause voltage surge or if it is less it will cause voltage dips. For proper operation of the system, synchronization must be kept with the load. The power grid can withstand a single event that is a single generator failure or a single transmission line failure. This is called as N-e contingency planning. The system can collapse if several failures take place in rapid succession.
Theory related to project work
If generator 1 load demand will increase then we have to share the load. So for that we are doing load sharing in which some amount of load will be shared on another generator 2.
If load demand is increasing out of capacity in that condition we have to use load shading in which all overload will be a disconnect from generator and generator will be safe.
During shading, condition PLC gives a signal in that condition all load work on the external source for some time. After that when the healthy condition occurs then all load transfer to the system alternator and backup system automatically out from system.
We occurring fault manually. In that condition, if fault occurs in a particular line then it indicates on SCADA and which fault occurs is also shown.
PLC compares the reference value of the main alternator and connects to the second alternator through relay according to reference voltage Designing an efficient and cost-effective solution for replacing or changing the alternator that is Problem-related to the alternator when it failed then it can be handle and control by PLC.
With a Programmable Logic Controller (PLC) scheme, load shedding is initiated based on the total load versus the number of generators online and/or detection of under-frequency conditions. Each substation PLC is programmed to initiate a trip signal to the appropriate feeder breakers to shed a preset sequence of loads.
In this work, fault detection and diagnostic module is described based on internal PLC program signal data which is acquired through OPC Server. The observed or real-time PLC signal data is compared with normal PLC signal data to find out possible faults or deviations. The data acquisition procedure and the techniques used have been explained in this paper.
According to the International Electrotechnical Vocabulary, a backup protection scheme is intended to operate when a power system fault is not cleared or an abnormal condition is not detected in the required time because of failure or inability of other protection to operate or failure of the appropriate circuit breaker to trip. The backup system is, by definition, slower than the main protection. A backup system may be obtained automatically as an inherent feature of the main system scheme, or separately by means of additional equipment.
There are 3 lamp as shown in the simulation which is considering as load of each ALTERNATOR, which are interconnected.
As shown in simulation Generator 1, 2 and 3 are supplying the power to the lamp 1,lamp 2 and lamp 3 through grid.
Load demand is balanced by using PLC through which load sharing, load shading and backup condition is possible.
If generator 1 load demand will increase then we have to share the load. So for that we are doing load sharing in which some amount of load will be shared on another generator 2.
If load demand is increasing out of capacity in that condition we have to use load shading in which all over load will be disconnect from generator and generator will be safe.
During shading condition PLC gives a signal in that condition all load work on the external source for some time. After that when healthy condition occurs then all load transfer to the system alternator and backup system automatically out from system.
We occurring fault manually. In that condition if fault occurs in particular line then it indicates on SCADA and which fault occurs is also shown.
They can be designed for multiple arrangements of digital and analog I/O extended temperature ranges, resistance and vibrations and impact etc.
This function is discrete inputs are given a unique address and PLC instruction can test if the inputs state is on or off.
A Programmable Controller is a specialized computer. Since it is a computer, it has all the basic component parts that any other computer has; a Central Processing Unit, Memory, Input Interfacing and Output Interfacing. A typical programmable controller block diagram is shown above.
After the planning phase of the design, the equipment can be ordered. This decision is usually based upon the required inputs, outputs and functions of the controller. The first decision is the type of controller, mini, micro, or software-based. This decision will depend upon the basic criteria listed below.
Memory - Often 1K and up. The need is dictated by the size of the ladder logic program. A ladder element will take only a few bytes, and will be specified in the manufacturer's documentation.
A number of special I/O modules - When doing some exotic applications, a large number of special add-on cards may be required.
Scan Time - Big programs or faster processes will require shorter can times. And, the shorter the scan time, the higher the cost. Typical values for this are 1 microsecond per simple ladder instruction
Communications - Serial and networked connections allow the PLC to be programmed and talk to other PLCs. The needs are determined by the application.
Software - Availability of programming software and other tools determines the programming and debugging ease.
The process of selecting a PLC can be broken into the steps listed below.
Understand the process to be controlled (Note: This is done using the design sheets in the previous chapter).
If not already specified, a single vendor should be selected. Factors that might be considered are, (Note: Vendor research may be needed here.)
Plan the ladder logic for the controls. (Note: Use the standard design sheets.)
Count the program instructions and enter the values into the sheets
Then that output of converter gives to the analog to digital converter of PLC. It converts ampere value in terms of digital data because PLC read digital data. We give up to 200ma to the PLC which is converted by the converter.
In our panel, we are using 5:1 C.T. and it gives the output to the converter.
This Converter input is 0-5 Amp and output is 0-20ma. And 24DC/230AC input and 0-10 AC/DC output.
It gives data to PLC Analog to Digital Converter and as predetermined data plc operate the function of load sharing, load shading.
Relay are switches that open and close circuits electromechanical. Relay control one electrical circuit by opening and closing contacts in another circuit.
When a relay contact is Normally open(NO), there is an open contact when the relay is not energized. When a relay contact is Normally closed(NC), there is a closed contact when the relay is not energized.
In either case, applying an electrical current to the contacts will change their state. Relays are generally used to switch smaller currents in a control circuit and do not usually control power consuming devices except for small motors, LED lamps.
Nonetheless, relays can "control" larger voltages and amperes by having an amplifying effect because a small voltage applied to a relay coil can result in large voltage being switched by the contacts.
Protective relays can prevent equipment damage by detecting electrical abnormalities, including overcurrent, overload and reverse currents.
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There are many applications for PLCs in substation automation, distribution automation, and SCADA systems. As utility engineers become more familiar with the capability of PLCs and PLC manufactures to develop new substation specific products, the number, and type of potential
With the application of this protection system in an existing power system results in less prone to blackout or brownout conditions.
Load sharing, Load shading easily applicable in the system. The fault is also analyzed by this panel. If shading occurs then Power backup is applied instantly.
So for the power continuity of the supply without any load shading condition, this system will apply.
By using PLC and SCADA all over system will fully automatic control, Load sharing will be accurate share in all alternators; load shading will occur at the instant therefore no damage to the alternator.
This system is also applicable at the industrial sector as well as the commercial sector. At which high amount of load supply and large amount of working process at every time.
By using PLC and SCADA in the system fault will easily detect and solve at the instant. And in faulty condition power continuity is ease from another side and getting time to remove the fault.
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Tripping in electricity supply. (2019, Nov 15). Retrieved from https://studymoose.com/tripping-in-electricity-supply-essay
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