The primary types of protective systems are sloping, benching, shoring, and shielding
What are the types of protection schemes?
It is a usual practice to divide the Types of Protection scheme into two classes viz. primary protection and back-up protection. 1. Primary Protection: It is the protection scheme which is designed to protect the component parts of the power system. Thus referring to Fig. 21.29, each line has an overcurrent relay that protects the line.
What are the two types of protection under the Power Act?
When a fault occurs on any part of electric power system, it must be cleared quickly in order to avoid damage and/or interference with the rest of the system. It is a usual practice to divide the Types of Protection scheme into two classes viz. primary protection and back-up protection.
What is primary protection?
Primary Protection: It is the protection scheme which is designed to protect the component parts of the power system. Thus referring to Fig. 21.29, each line has an overcurrent relay that protects the line.
What are the different types of secondary or backup protection?
Types of Secondary or backup protection 1 Relay Backup Protection 2 Breaker Backup Protection 3 Remote Backup Protection 4 Centrally Co-ordinate Backup Protection More ...
What are protective systems?
Protective system means a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures.
What are the three main protection methods?
There are three primary protection methods that are used in excavation: shielding, sloping and benching....Three Primary Protection Methods In ExcavationThe angle of the slope,The type of soil,The depth of the trench, and.The weather conditions all need to be taken into account.
What are the 3 main protection methods against cave-ins?
To prevent cave-ins: SLOPE or bench trench walls. SHORE trench walls with supports, or. SHIELD trench walls with trench boxes.
What are some types of protective systems that can be used in an excavation?
When figuring out what the best method is for protecting works in excavations there are four common methods. Those methods are sloping, benching, and shoring or shielding. Sloping: Sloping is a viable option as a protective system.
What are the three main protection methods against cave-ins quizlet?
OSHA requires that all excavations in which employees could potentially be exposed to cave-ins be protected by one or more of the following three methods: Sloping, benching, shoring, and shielding.
What are cave-in protection systems?
Use sloping, benching, shoring and shielding to provide cave in protection on an excavation site. There are four ways to protect workers from cave ins on an excavation site: sloping, benching, shoring and shielding.
What are the 4 categories priorities of OSHA inspection?
EHS Insider BlogImminent Danger has top priority. ... Fatalities and Catastrophes are next in priority. ... Complaints and Referrals are OSHA's third priority. ... Programmed Inspections are the fourth priority.
What are two ways to protect an excavation?
Methods of ProtectionSloping and Benching. This method is considered the safest of the four methods. ... Timber shoring. This method requires installing aluminum hydraulic, pneumatic, other types of supports to shore up the trench face prevent movement of soil.Shielding. ... Engineered design.
What is a shoring system?
Shoring is commonly used when installing the foundation of a building. A shoring system such as piles and lagging or shotcrete will support the surrounding loads until the underground levels of the building are constructed. Commonly used shoring equipment includes post shores, shoring beams, and timber jacks.
Which type of protective system involves digging the excavation into several layers or levels?
BenchingThere are different types of protective systems. Benching means a method of protecting workers from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near- vertical surfaces between levels.
What is the most common protective measure used in pipeline trenching?
Today, shield systems are probably the most commonly used protective systems in the field, and they have come a long way in terms of the features they offer.
What is excavation protection?
Excavation Safety is a standardized set of safety precautions for trenching and excavation to eliminate hazards and control risks in compliance with regulations. It is also referred to as Trenching and Excavation Safety as often cited by the U.S. Occupational Safety and Health Administration (OSHA).
What are the methods of protection?
There are three basic methods of protection—explosion containment, segregation and prevention.
What is primary protection?
Primary protection was introduced, alongside enhanced protection, in April 2006. Its purpose is to protect those who still had uncrystallised pensions at 6 April 2006 (A-Day) from the full impact of the lifetime allowance (LTA) tax charge.
What are the three basic components of a protective relay scheme?
Relay Circuit DiagramThe first part is the primary winding of a current transformer (C.T.) ... The second part consists of the secondary winding of the current transformer and circuit breaker and the relay operating coil.The third part is the tripping circuit which may be either Ac or DC.
What are the different protections for electrical system?
Some examples of electrical protection devices are lightning arresters, surge protectors, fuses, relays, circuit breakers, reclosers, and other devices. Every electrical circuit has a maximum voltage or amperage. If this value is exceeded, the wire will overheat, causing the wire insulation to melt and fire to ignite.
What is a structure that supports the sides of an excavation and which is designed to prevent cave-ins?
A structure that supports the sides of an excavation and which is designed to prevent cave-ins : Shoring
What are the different types of shoring?
The basic types of shoring : Timber and aluminum shoring
What is a natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed?
A natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed : Stable rock
What is power system protection?
Below is the power system protection scheme which is designed to protect the power system parts and components. As shown in below fig, each line associated with over current relay that protect the lines from faults. So, if a fault happens on any line, it will be cleared by its relay and circuit breaker. This is called primary or main protection and acts as a first line defender. The service record of primary relaying is very high with well over 90% of all operations being correct. But this is not always the case, sometimes faults are not illuminated by the primary or main protection system i.e. circuit breaker and relay system because of trouble within the relays, circuit breakers or wiring system in different conditions. In those conditions, Secondary or backup protection system does the required job.
Why is secondary protection not possible?
As we know that, it is not possible to design a 100% secure and efficient system because there are possibilities of failure in the connected CTs, PTs, circuit breaker etc. in the system. If it happens, then it will destroy our whole switching system.
Is a larger part disconnected when primary relaying functions correctly?
In addition, a larger part is disconnected then when primary relaying functions correctly. Therefore, greater emphasis should be placed on the better maintenance of primary relaying which is economical.
What is primary protection in alternators?
In the case of alternators, primary protection is provided to the stator, by percentage differential protection or by restricted earth-fault protection, etc. The backup protection is provided by over-current protection and earth-fault protection. Of course, these backup protection schemes are not for the backup of the primary protection of the stator. Instead, they operate for faults when the corresponding protection system fails to isolate the fault. The figure below shows the operation of primary and backup protection schemes.
What is backup protection?
If due to some reasons, primary protection fails, additional protection is generally provided called backup protection. The backup protection is the substitute for the primary protection and isolates the faulty section from the healthy one. The primary protection may fail due to any of the following reasons,
What relays are used to isolate a faulty circuit breaker?
The relays R 3, R 2, and R 1 are graded with enough time lag sequentially. Thus, the operation relays R 3, R 2, and R 1 to isolate the faulty section is due to backup protection.
What is the duty of the primary relay?
If any fault occurs in a protected zone, it is the duty of the primary or main relays to act and isolate the faulty element. Primary protection is one, which immediately senses and responds to the fault. It will take an instantaneous action in order to isolate the faulty part from the healthy part of the power system.
