High Voltage Circuit Breakers

  • Electrical power transmission networks are protected and controlled by high-voltage breakers.
  • SF6 gas filled and spring mechanism operated CBs are widely used in modern EHT systems
  • Basic operating principle of these breakers does not vary from any other LV or MV CBs
  • Sulphur hexafluoride (SF6) gas is a good arc quenching medium due to its low ionization property
  • SF6 has good insulation properties too
  • The chambers and the supporting hollow insulators are filled with SF6 gas
  • In the previous picture, the breaker is operated using a gang operated single mechanism box
  • CBs with separate operating mechanism box for each pole are also in use.High Voltage Circuit Breakers
SF6 High Voltage Circuit Breakers

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AutoCAD Electrical 2013 Service Pack 1

You can apply this update to AutoCAD Electrical 2013 running on all supported operating systems and languages. 


Be sure to install the correct update (32-bit or 64-bit) for your software and operating system.

The Readme contains the latest information regarding the installation and use of this update. It is strongly recommended that you read the entire document before you apply the update to your product. For your reference, you should save the Readme to your hard drive or print a copy.

This Service Pack can be applied to AutoCAD Electrical 2013 installed as a standalone application as well as AutoCAD Electrical 2013 installed from Autodesk Product Design Suite 2013.

Ace2013_SWL_SP1.exe (exe – 23053Kb)

Ace2013_SWL_SP1_x64.exe (exe – 29499Kb)



Initiate site activities in scope of site management

Project management group and O and M management group plan various preparatory activities to meet L1 demands These include ;

  • Acquiring land,right off way for line/land               – Schedule for finalizing subcontracts
  • Case inflow and case outflow schedule                            – Billing schedule
  • Schedule for training
  • Schedule of submission of drawing documents,check lists to site
  • Schedule of equipment delivery to site
  • Schedule for inputs from the other sources (Governments agencies ,land owners,main customers etc )
  • Communication facilities,telephones,telex,wireless,fax,internet,radio communication,power line carrier communication
  • Personal computer facility and networking .                – Survey of transportation route
  • Insurance policies for plant equipment and third party for ETC phase and O and M phase
  • Schedule for safety facilities                           – Schedule for safety procedures
  • Schedule for site organization and manning for ETC phase and O and M phase
  • These schedules are also monitored on monthly basis

ANSI / IEEE Codes for Protection Functions

ANSI / IEEE Codes for Protection Functions
Code
Function Description
Application Area
Feedes
Transformers
Generators
Motors
Cap. Banks
2
Time delay
x
x
x
x
x
12
Over speed
x
x
21
Impedance Relay (Distance Protection)
x
x
21G
Distance Relay – earth Fault
24
Over excitation
x
x
25
Synchronising check
x
x
26
Over / under temperature
x
x
x
27 / 59
Under voltage / Over Voltage – ac
x
x
x
x
x
30
Annunciator
x
x
x
x
x
32
Reverse Power (Directional Power)
x
x
32P
Reverse Power (Directional Power) – Active
x
x
32Q
Reverse Power (Directional Power) – Reactive
x
x
37
Under Power / Under curent
x
x
38
Bearing Temperature
x
x
39
Bearing Vibration
x
x
40
Loss of field
x
x
43
Manual transfer switch
x
x
45
DC Over voltage
x
46
Reverse phase / phase balance current relay
x
x
x
x
x
47
Phase sequence / phase reversal voltage
x
x
x
49
Thermal Over load
x
x
x
x
50
Instantaneous Over Current
x
x
x
x
x
50N
Instantaneous Earth Fault
x
x
x
x
x

OPERATION INDICATOR

 Generally, a protective relay is provided with an indicator that shows when the relay has operated to trip a circuit breaker. Such “operation indicators” or “targets” are distinctively colored elements that are actuated either mechanically by movement of the relay’s operating mechanism, or electrically by the flow of contact current, and come into view when the relay operates. They are arranged to be reset manually after their indication has been noted, so as to be ready for the next operation. One type of indicator is shown in Fig. 2. Electrically operated targets are generally preferred because they give definite assurance that there was a current flow in the contact circuit. Mechanically operated targets may be used when the closing of a relay contact always completes the trip circuit where tripping is not dependent on the closing of some other series contact. A mechanical target may be used with a series circuit comprising contacts of other relays when it is desired to have indication that a particular relay has operated, even though the circuit may not have been completed through the other contacts.

FUNDAMENTAL RELAY-OPERATING PRINCIPLES AND CHARACTERISTICS

Protective relays are the “tools” of the protection engineer. As in any craft, an intimate knowledge of the characteristics and capabilities of the available tools is essential to their most effective use. Therefore, we shall spend some time learning about these tools without too much regard to their eventual use.

GENERAL CONSIDERATIONS

All the relays that we shall consider operate in response to one or more electrical quantities either to close or to open contacts. We shall not bother with the details of actual mechanical construction except where it may be necessary for a clear understanding of the operation. One of the things that tend to dismay the novice is the great variation in appearance and types of relays, but actually there are surprisingly few fundamental differences. Our attention will be directed to the response of the few basic types to the electrical quantities that actuate them.

OPERATING PRINCIPLES

There are really only two fundamentally different operating principles:
(1) electromagnetic attraction, and
(2) electromagnetic induction.

Electromagnetic attraction relays operate by virtue of a plunger being drawn into a solenoid, or an armature being attracted to the poles of an electromagnet. Such relays may be actuated by d-c or by a-c quantities. Electromagnetic-induction relays use the principle of the induction motor whereby torque is developed by induction in a rotor; this operating principle applies only to relays actuated by alternating current, and in dealing with those relays we shall call them simply “induction-type” relays.

HOW DO PROTECTIVE RELAYS OPERATE?

Thus far, we have treated the relays themselves in a most impersonal manner, telling what they do without any regard to how they do it.

 This fascinating part of the story of protective relaying will be told in much more detail later. But, in order to round out this general consideration of relaying and to prepare for what is yet to come, some explanation is in order here.

All relays used for short-circuit protection, and many other types also, operate by virtue of the current and/or voltage supplied to them by current and voltage transformers connected in various combinations to the system element that is to be protected. Through individual or relative changes in these two quantities, failures signal their presence, type, and location to the protective relays. For every type and location of failure, there is some distinctive difference in these quantities, and there are various types of protective-relaying equipments available, each of which is designed to recognize a particular difference and to operate in response to it

More possible differences exist in these quantities than one might suspect. Differences in each quantity are possible in one or more of the following:

A. Magnitude.
B. Frequency.
C. Phase angle.
D. Duration.
E. Rate of change.
F. Direction or order of change.
G. Harmonics or wave shape.

Then, when both voltage and current are considered in combination, or relative to similar quantities at different locations, one can begin to realize the resources available for discriminatory purposes. It is a fortunate circumstance that, although Nature in her contrary way has imposed the burden of electric-power-system failure, she has at the same time provided us with a means for combat.

Fig. 5. Illustration for Problem 2.

THE EVALUATION OF PROTECTIVE RELAYING

Although a modern power system could not operate without protective relaying, this does not make it priceless. As in all good engineering, economics plays a large part. Although the protection engineer can usually justify expenditures for protective relaying on the basis of standard practice, circumstances may alter such concepts, and it often becomes necessary to evaluate the benefits to be gained. It is generally not a question of whether protective relaying can be justified, but of how far one should go toward investing in the best relaying available.
Like all other parts of a power system, protective relaying should be evaluated on the basis of its contribution to the best economically possible service to the customers. The contribution of protective relaying is to help the rest of the power system to function as efficiently and as effectively as possible in the face of trouble.2 How protective relaying does this is as foIlows. By minimizing damage when failures occur, protective relaying minimizes:
A. The cost of repairing the damage. 
B. The likelihood that the trouble may spread and involve other equipment. 
C. The time that the equipment is out of service. 
D. The loss in revenue and the strained public relations while the equipment is out of service.
By expediting the equipmentÕs return to service, protective relaying helps to minimize the amount of equipment reserve required, since there is less likelihood of another failure before the first failure can be repaired.
The ability of protective relaying to permit fuller use of the system capacity is forcefully illustrated by system stability. Figure 4 shows how the speed of protective relaying influences the amount of power that can be transmitted without loss of synchronism when short circuits occur.4 More load can be carried over an existing system by speeding up the protective relaying. This has been shown to be a relatively inexpensive way to increase the transient stability limit.5 Where stability is a problem, protective relaying can often be evaluated against the cost of constructing additional transmission lines or switching stations.
Other circumstances will be shown later in which certain types of protective-relaying equipment can permit savings in circuit breakers and transmission lines.
Fig. 4. Curves illustrating the relation between relay-plus-breaker time and the maximum amount of power that can be transmitted over one particular system without loss of synchronism when various faults occur.

The quality of the protective-relaying equipment can affect engineering expense in applying the relaying equipment itself. Equipment that can still operate properly when future changes are made in a system or its operation will save much future engineering and other related expense.

One should not conclude that the justifiable expense for a given protective-relaying equipment is necessarily proportional to the value or importance of the system element to be directly protected. A failure in that system element may affect the ability of the entire system to render service, and therefore that relaying equipment is actually protecting the service of the entire system. Some of the most serious shutdowns have been caused by consequential effects growing out of an original failure in relatively unimportant equipment that was not properly protected.

UNDESIRED TRIPPING VERSUS FAILURE TO TRIP WHEN DESIRED

Regardless of the rules of good relaying practice, one will occasionally have to choose which rule may be broken with the least embarrassment. When one must choose between the chance of undesired or unnecessary tripping and failure to trip when tripping is desired, the best practice is generally to choose the former. Experience has shown that, where major system shutdowns have resulted from one or the other, the failure to tripÐor excessive delay in tripping-has been by far the worse offender.

PROTECTIVE RELAYING VERSUS A STATION OPERATOR

Protective relaying sometimes finds itself in competition with station operators or attendants. This is the case for protection against abnormal conditions that develop slowly enough for an operator to have time to correct the situation before any harmful consequences develop. Sometimes, an alert and skillful operator can thereby avoid having to remove from service an important piece of equipment when its removal might be embarrassing; if protective relaying is used in such a situation, it is merely to sound an alarm. To some extent, the preference of relying on an operator has a background of some unfortunate experience with protective relaying whereby improper relay operation caused embarrassment; such an attitude is understandable, but it cannot be supported logically. Where quick and accurate action is required for the protection of important equipment, it is unwise to rely on an operator. Moreover, when trouble occurs, the operator usually has other things to do for which he is better fitted.