Chapter 1: Working on Lines and Equipment - Working on the Line - Possible Test Questions - Week 7 Flashcards
Categories of linework:
- Construction
- Maintenance
- Repair
The two methods for working on a power delivery system:
- Energized
- De-energized
List a few specialized live-line tools:
- Hot Sticking
- Rubber Gloving (Including use of rubber sleeves)
- Barehanding
OSHA Linework is governed by:
- Construction or general industry regulations
De-Energized work involved protection against both:
-Normal and abnormal sources of energy
Proper steps to de-energize:
- Disconnect
- Test
- Properly Ground
The two grounding procedures:
- Equipotential Zone (EPZ)
- Bracket Grounding
Equipotential Zone (EPZ) Grounding:
- Grounding is the preferred method for protecting the lineworker
Bracket Grounding:
- Is used to trip out the circuit as quickly as possible
The terms “voltage” and “potential” will be:
- used interchangeable throughout this course
Current will divide and take:
- every available path to objects of different potential
Insulate and Isolate:
- The only way to completely prevent current flow through the lineworker
Protective grounding and bonding are effective if they meet the following two objectives:
- Minimize the time it takes to trip the circuit
- Limit the current flow and voltage drop across the lineworker’s body.
When performing energized work, lineworkers follow three principals to manage current:
- 1) Insulate-use hot sticks, rubber gloves/sleeves, and rubber/plastic cover-up equipment to shield against current flow.
2) Isolate-create physical separation from any object of different potential. For example, an insulated aerial lift or insulated platform helps to isolate the worker’s feet from differences of potential. - 3) Protect against second point of contact-arrange the insulation and isolate the workers and tools so that anything that has a different potential than the item to be worked cannot be reached from the work position.
The second point of contact is defined as:
- “the point at which current leaves
the body during simultaneous contact between two or more objects of
different potential.”
The Pain Scale:
- DETECTABLE: (1-5 milliamps (mA) OR .1%-.5% of 1 amp) Feeling of warmth or a slight tingle; little or no body reaction.
- PAINFUL: (9-15 mA OR .9%-1.5% of 1 amp) Feeling of clear discomfort; minor body movement.
- LET GO: (16-100 mA OR 1.6%-10% of 1 amp) Instant pain; immediate letting go or moving away from the contact.
- VENTRICULAR FIBRILLATION OF THE HEART (V-FIB): (100-700 mA OR 10%-70% of 1 amp): Disabled; heart is unable to function properly.
- BURNING OF THE SKIN AND ORGANS: (1 amp and higher) Significant damage
All Employees exposed to electrical hazards must use approved:
- protective equipment
- OSHA
Clearance:
- Disconnecting a line, line section, or equipment that is being worked on
A clearance typically involves three roles:
- The Clearance Holder
- The System Operator
- The Field Operator
The clearance holder:
- is responsible for accomplishing the work in the field (normally a crew leader). A clearance is issued to the clearance holder, and cannot end until the clearance holder releases the clearance.
The system operator:
- works at the utility’s operations center and has a system-wide perspective and control of the system in real time. This person gives permission for the clearance to occur, can operate devices remotely, and releases the line or apparatus to the clearance holder so that the work can be performed.
A field operator:
- is any employee in the field who is physically operating the apparatus or devices used to disconnect the lines or equipment. This is done at the direction of the system operator. This employee could be a troubleman, switchman, roving operator, station operator, or other position.
The clearance holder may perform the duties of the:
- field operator
Three major objectives when clearing lines and equipment:
- Ensure the safety of all employees and the public
- Minimize the negative impact on the electrical system
- Minimize the number of customers who will be out of service
Clearance Procedure:
1) Clearance Holder: Create clearance plan and confirm details.
2) Clearance Holder: Request clearance in writing.
3) System Operator: Approve clearance and create a switching order.
4) Field Operator: Disconnect, lock, and tag all normal sources of energy.
5) System Operator: Establish and issue clearance.
6) Clearance Holder: Test and apply protective grounds. Complete the work.
7) Clearance Holder: Verity work is completed. Release the clearance.
8) System/Field Operator: Return the system to normal.
CLEARANCE POINTS
- Refers to any device used to disconnect a line or piece of equipment from a normal source of energy-switches, disconnects, jumpers, connectors, terminations, and other devices.
A visual clearance point:
provides a clear visual gap between the source and load terminals of a device.
A non-visual clearance point:
- is any type of enclosed equipment. Even when the contacts are open, they are not visible from outside of the enclosure.
Air Switch:
- Air switches are gang-operated, which means the moving parts are connected so that all three phases operate simultaneously with one action by the operator. Air switches may be operated by a manual hook, manual handle, or motor.
Single-Blade Disconnect (Cutout):
- Many types of disconnects are used as clearance points-for both line and substation clearances.
Open Jumper:
- Used on both primary and secondary circuits, open jumpers, open loops, and open taps are common clearance points. (A jumper is a piece of conductor used to complete an electrical circuit.)
Line Recloser:
- Line reclosers are widely used as clearance points. In addition to the line recloser being open, most companies require a separate clearance point in the form of open jumpers, disconnects, or air switches.
Flying Bells (Inline Sectionalizer)
- Also known as a span open, this type of clearance point can be installed at various locations to minimize the number of customers who will be out of service.
All devices used as a clearance point, must be tagged. This includes:
- physical switches and automatic or remote control switches.
OSHA requires that the tag have an unlocking strength of at least __lbs.
50
Induced Voltage (Induction):
- Induction occurs when a nearby energy source-such as an energized transmission line-electrifies a disconnected and de-energized conductor or conductive object. The more current flowing through the energized conductor, the more intense the induction is on the de-energized conductor.
Capacitance:
- Equipment designed to store electricity may retain a charge long after being disconnected.
Static Charge
Warm winds blowing across the surface of conductors can create a static charge on the conductor. The amount of that charge depends on the size of conductor, length of the line, wind direction, and temperature.
Wait ____ minutes before installing grounds on a disconnected capacitor.
- five
Fault current:
The amount of current that a given system can deliver to a short circuit, also known as a fault.
The grounding components used on transmission lines must be large enough to handle:
- the increased fault current.
Step Potential:
- Is the voltage difference between the worker’s two feet.
Touch Potential:
- Is the voltage difference between the worker’s hand (contacting an energized object) and the place they are standing.
Protective grounds, insulating equipment, and restricted work areas help:
- protect employees on the ground.
Step and touch potentials are:
- hazardous to workers on the ground.
Bonding:
- Connecting any conductive item within the work space to the same potential as the grounded phases.
Barricade vehicles at all times to prevent:
- unauthorized access to the work area.
