4th step questions
What size grounds would b~ applied for work on a 16 kV circuit with 9 kA fault duty?
#2 AWG
What is the working load limit of a hand line sheave?
1,000 lbs
What is the maximum weight atlowable for a 2-1\2) transformer bank hung on a wood po!e using a transformer bracket?
1,600 lb total weight limit.
All employees must be belted off while climbing wood poles. What are the 3 exceptions?
1. Free Climbing shall be allowed to first pole step. Maximum 15 ft head height. 2. Free climbing shall be allowed when utilizing pole steps. 3. Free climbing shall be allowed when obstructions prohibit using a safety.
list the overhead grounding schemes in order of preference
1. Parallel 2. Balanced 3. Unbalanced
Describe the symptoms of shock.
1. The shock victim's behavior may range from a feeling of restlessness or agitation to stupor and unconsciousness. 2. The pulse rate will be weak or almost imperceptible; it may retain either a regular or irregular rhythm. 3. Other physical symptoms may be: a. The face may be pale or ashen. b. The skin may feel cool and clammy with increased perspiration. c. Pupils may be dilated or unequal in size and will lack luster. d. Dizziness, nausea and vomiting may occur. e. Unconsciousness may develop. f. Breathing may be shallow or stop. g. The heart may stop beating.
Which type and size of fuse is used to test a 100 kVA, 12 kV transformer with SM0-20 fuse holders? Is this fuse current limiting?
10 AX-limiter. Yes, it is current limiting.
What is the minimum height a pole band must be installed on a pole?
12 feet from ground level.
What equipment is needed to load check an RO transformer?
2 Potential Transformers (PT} 2400/120 V One Ammeter 1 Voltmeter
If two 10 kVA transformers are wired in an open-delta configuration -for 3-phase power -what would be the available kVA?
20 kVA x 0.86 = 17.2 available kVA.
Haw is a PT typically connected in a 2400 V application, and what is the typical turns ratio for this PT?
2400 V PTs are normally phase-to-ground connected. The typical turns ratio is 20:1.
What is the maximum allowable difference in impedance between transformers within a bank?
25%
What is the primary coil voltage of a wye-connected transformer bank installed on a 4 kV circuit?
4 kV= 4,160 V -:--1.73 = 2,400 V
What is the maximum weight allowable for a closed-delta 300 kVA transformer bank on a SO-foot wood pole using a transformer mounting bracket? What is the minimum diameter pole for this application?
4,200 lbs. 11 inch minimum diameter.
What is the minimum distance from the top of the pole to the first through-bolt hole on a new 40-foot pole?
6 1/2 inches
What is the safe working load limit of a 1-1/8" 2-in-1 double braid polyester core and ~ . ...,, cover winch line? f
7,000 lbs
In a three-phase circuit, what is a grounded leg? Where is it located ln the customer's panel?
A grounded leg is a phase that has been grounded. lt is generally located in the middle position in the customer's pane!.
What is a high legl How is it identified?
A high leg is the secondary phase with the highest phase to ground voltage. As required by the National Electric Code, the high phase (power leg) must be prominently identified by orange markings on the cable or bus.
Upon entering an underground structure, an employee observes evidence of structural compromise, and flexing concrete. According to the DOM, what actions shall the employee take?
A. Employees will inform their immediate supervisor. B. Employees will mitigate the hazard to the extent possible, which may include installing remote switching or other isolation methods. C. The supervisor in charge will notify the Switching Center of the condition and that a temporary "CAUTION DO NOT ENTER WHILE EQUIPMENT IS ENERGIZED" sign was posted, and will prepare a circuit map revision noting the structure is "Closed When Energized."
What are the two poiarities a transformer can have?
Additive and subtractive.
Explain APM Rule 307, "Moving Underground Cable."
All in-service cabtes that are to be moved shall be carefuliy inspected before and after moving. b. Cables energized in excess of 600 volts shall be moved only under the direction of the supervisor or employee in charge.
How is rotation checked/determined?
At the customers panel using a phase sequence indicator, from L to R (RWB) attach clips to customer's phases.
If it is necessary to climb through a pole-mounted capacitor installation, what actions must be taken beforehand?
Before climbing into or through the area of a capacitor installation, automatically switched capacitors shall be de-energized and the controls made inoperative. On non-automatically switched capacitor instai!ations, contact shall not be made with pole top apparatus as specified in Rule 205 Oi other metal hardware in the area of an energized capacitor instaJlatfon.
What must be done prior to closing the secondary leads on a 120/240 V 3¢ 4-wire delta overhead transformer bank?
Before closing secondary delta leads, verify that the voltage across is less than 20 V. This connection between the leads must be made on the secondary rack.
Describe how and-when to shunt CT Secondaries.
Before working on instruments or other devices in a current transformer secondary circuit, the instruments or devices shall be short-circuited by jumpers or approved test switches, so that the current transformer secondary circuit cannot be opened while working on the instruments or devices connected thereto.
What is the general function of ground relays?
Both, directional and non-direction, ground overcurrent relays are used in a wide range of ground protection applications to sense a ground fault condition on lines and equipment at all voltage levels.
What is the maximum tank temperature for a transformer?
By design, the maximum internal temperature rise in a transformer at full load can be 115 °F (65 °C}; this can increase to a 155 °F (88 °C) rise at 160 percent of rated load. Under no circumstances should the maximum tank temperature (ambient plus tank temperature rise) exceed 265 °F (130 ·q.
What are current transformers (CTs) and potential transformers {PTs)? What are their typical applications in distribution circuits?
CTs are transformers which reduce high currents to safe levels for relay protection and metering services. PTs are transformers which reduce high voltage levels to safe levels for equipment operation and metering services.
According to the APM, when may underground cable be considered de-energized?
Cable and equipment shall be considered energized and worked with adequate protective devices until it has been tested de-energized with an approved device for indication of voltage and grounded with approved ground devices.
Which sizes of conductors are used for single-phase lighting secondaries?
Ceitain sizes of conductors are most commonly used for lighting secondaries: 1/0 aluminum or #2 copper in all residential areas except those designed for minimum service, and 4/0 aluminum or 2/0 copper where the initial installation requires transformers larger than 25 kVA.
When are clearances required?
Clearances are required to work on de-energized generating station or substation apparatus or equipment which is normally energized above 600 volts. Clearances are required to work on de-energized lines or line sections above 600 volts.
If a lineman has any doubt regarding the type or size of rigging equipment for a lift, what should they do?
Contact their supervisor
If a circuit has a total resistance of 15 0 and a current of 3 A, what is the voltage of the circuit?
E =Ix R E = 4 Ax 60 0 = 240 V
Concerning riser construction: no step or kick block shall be installed below what height on a pole?
Eight feet from a climbable surface.
Describe the operation of an RkVAh meter, based on different power factor loads.
For a lagging power factor load, the RkVAh meter will run forward if the phase rotation is correct and will try to run backward (backward rotation is prevented by a ratchet or detent on the disk shaft) if the phase rotation is incorrect.
When applying TS-5 to newly installed/relocated transformers, how are the transformer secondaries grounded (prior to energization).
For grounded secondaries, connect the secondary ground. For ungrounded secondaries, temporarily install a solid ground on the low side at any of the phase connections or the neutral. (The intent is to ensure enough fault-current to blow the test fuse for a primary to secondary fault.)
When making a lift with tackle blocks, how is friction accounted for?
For practical purposes, friction incurs a loss of approximately 10% for each sheave in rope blocks.
Why is it important that the correct size fuse be used in distribution circuits? What could result from installing a fuse that is either too weak or too heavy?
Fuses which are too weak may blow out during normal operatin& current loads. Fuses which are too heavy may fail to protect associated transformers (or other equipment).
Why is grounding performed?
Grounding is required for the protection of the worker when working on de-energized high-voltage lines or equipment. Use of personal grounds will minimize exposure associated with making ·contact with objects having hazardous difference of electrical potentials. Workers should avoid contact with applied grounds wherever possible to minimize exposure to hazardous conditions.
When is grounding required? When is it not required?
Grounding is required when working on a circuit that is normally energized above 600 V, unless other>Nise performing work with live iine or other approved insulated tools. Grounding is also required during wire stringing when high voltage sources are present. All conductors shall be considered energized until proven de-energized by testing and grounding. Grounding is not required when constructing a new line section on wood, composite, or concrete poles where there are no high voltage sources.
How much current would a 240 V heater, with 20 0 resistance, draw?
I = E+R l = 240V + 20 0 = 12 A
A 2000-watt electric heating unit is supplied by a 240 V circuit. What is the current drawn by the heater?
I= P+E I = 2000 W + 240 V = 8.33 A
Explain the APM Rule 309, as it applies to RAC switches.
If switching on a "RAC' type switch, a blocking device or special handle must be used to ensure that the switch is operated only to the desired position.
Describe the AC electrical characteristic of impedance.
Impedance is the total opposition to current flow in an AC circuit and is the combined effect of the resistance and the reactance in the circuit.
In an emergency, is it possible to modify or suspend APM rules? Explain.
In case of an emergency which may result in a serious personal injury, a supervisor, or employee in charge, may temporarily modify or suspend any of these ruies as may be considered necessary to permit proper handling of the specific emergency. In any such case, the person so acting shat! be fufly accountable for the reasonableness of these actions and for any accident or service interruption resulting therefrom.
In order to sag conductors properly, how is the appropriate sag chart determined?
In order to choose the sag table most suitable for the particular job at hand, determine the loading district (light or heavy loading) of the line location, the conductor to be used, and the pulling span of the line. Usually the elevation of the service center area traversed by the line, hence the kind of loading (light or heavy) conductor size and kind are known.
Are pole-mounted grounds allowed in the climbing space of rack construction?
No
Briefly explain APM Rule 147, Working Distance. What are the approach distances for 4 kV, 12 kV, and 16 kV circuits? May those distances be reduced?
No employee shall approach or take any conductive object, except with approved devices, closer to unprotected energized parts than shown in the following table: Approach distances may be reduced, provided adequate approved protective devices are used. Such protection shall be applied and removed with approved insulating devices. Contact shall not be made with protective devices on conductors energized above 7,500 volts except with live line tools. EXCEPTION: Employees certified in rubber gloving of conductors energized between 7,500 volts to 17 kV may contact protective devices up to 17 kV while wearing rubber gloves rated for the voltage and while utilizing "insulate and isolate" work practices.
Is it permissible for transformers with banked secondaries td be installed on either side of a switch? Explain
No. Primary lines sectionalizing devices shall not be located between transformers with banked secondaries
Is it permissible to provide a customer with both 3-wire and 4-wire service from the same transformer bank? Why or why not?
No. Do not connect 3-phase, 3 wire services to 3-phase, 4 wrre b_anks.
May PMHs or PM Es be used to de-energize capacitor banks? Explain.
No. PMH and PME switches cannot be used for capacitor switching, A sign reading "Capacitor Bank No. Source-Open Capacitor Bank Switch Before Opening This Switch" shall be placed on the compartment door of all PMH/PME switches used to feed capacitor banks.
When using a hand hoist, is it acceptab!e to use the chain and hook in a choker configuration? Why or why not?
No. The hook wili break under stress. A sling should be attached to the hoist hook.
What are the number of service drops allowed at one point of service, and what are the exceptions for no-or240-volt servJce??
Not more than one set of service drops will be installed by the Company to any one point-of-service delivery for any single-or multiple-occupancy building for the same voltage and phase classification, except as follows: 120/240 V Single Phase: \Nhere, for single-phase load only, with service delivery at 120/240 volts, the total load to be served employs sets of service-entrance conductors supplying groups of meter switches, main service switches, or meter switches supplied by individual set at service-entrance conductors, with aggregate capacity exceeding the maxim uni capacity which will be supplied by one set of ser"l!ce drops as specified in Paragraph 2.0 (page 2-5), the contractor shall _install two or three separate sets of service-entrance conductors as required thereon for the total load, and provide service terminating facilities for a separate service drop near each service head required. 240 V Single Phase: For 240 V single-phase power loads, the Company shall be consulted in each case relative to the required serving method. These loads may in some cases be supplied by one 3-phase service drop. ln any case, a separate set of service-entrance conductors for connection to a separate service drop may be required by reason of the Company's operating necessity.
List the high voltage sources, as defined by the grounding manual.
Open Breakers, Open Switches, Open Taps, or Open Fuses Crossings Backfeed Induction Static Charge
When -and why -is the wye leg tied, on the primary side of a 4 kV bank?
Open Wye banks (2 transformers) shalf be connected to the system neutral. Closed Wye-delta banks (3 transformers} shall not be connected to the system neutral. Tied for checking voltage. Wye-Wye banks (3 transformers) shall be connected to the system neutral.
As it appties to a current transformer {CT) used in metering, how is a CT's overload capability determined?
Overload capability is the ampere rating multiplied by the rating factor.
May PMHs or PM Es be used to de-energize capacitor banks? Explain?
PMH and PME switches cannot be used for capacitor switching. A sign reading "Capacitor Bank No. Source-Open Capacitor Bank Switch Before Opening This Switch" shall be placed on the compartment door of all PMH/PME switches used to feed capacitor banks.
What is the standard spacing for conductors, on a wood arm, for 12or16 kV 4-wire circuits? Also, what is the spacing between the neutral and inside phase?
Phase-to-Phase = 3 feet Phase-to-Neutral= 40 inches minimum
How must the photocells/photoelectric controller for streetlights be oriented when installed?
Photoelectric controller must be installed so photocell is exposed to the north sky.
In general, where are high voltage signs installed on crossarms and poles?
Poles or crossarms shall be marked with approved HIGH VOLTAGE signs. Wherever possible, HIGH VOLTAGE signs shall be placed on the pole at the lowest level of line conductors energized in excess of 750 V, which indicates that all circuits above that level are HIGH VOLTAGE. No additional HIGH VOLTAGE signs are necessary. As an alternate to marking poles, HtGH VOLTAGE signs shall be placed on all crossarms supporting line conductors energized in excess of 750 V.
A dip-on ammetei ieads 7 A en a 120 V conductor. What is the resistance?
R:: E+l R=120V+7A=17.10
How are SCE and factory-installed test blocks wired?
SCE-insta!!ed test blocks are connected in a line-line-line, foad-load-!oad wiring sequence. Factory (or contractor) installed test blocks are connected in a line-load, line-load, line-load wiring sequence
For what type of street lighting system are constant-current (regulated output (RO)) transformers used.
Series streetlight circuits are supplied by constant current or Regulated Output (RO) transformers which deiiver a constant current of 6.6 A.
Which two electrical ratings are used when determining ground size(s)?
Source voltage and fault-current duty at the worksite or source substation(s).
What is the difference between a straddle tap and a standard tap?
Straddle: 5% up and 5% down Standard: 10% down
What are the three basic nylon sling hitches?
Straight Pull Choker Hitch Basket Hitch
What is the continuous current rating and interrupting rating of the G& W Viper Automatic Recloser?
The G&W Viper-SAR has a continuous current rating of 600 amps and an interrupting rating of 12.5 KA symmetrical
When should the automatic circuit recloser be made non-automatic in underground distribution circuits?
The automatic circuit re closer on the circuit being worked shall be made non-automatic when: 1. Splicing or patching energized high-voltage underground cable. 2. Relocating energized high-voltage underground cable or equipment. 3. Filtering or replacing oil on energized high voltage underground equipment. 4. Operating energized load break components. S. When employees are working inside an underground structure to make repairs immediately following a high-voltage failure, the automatic recloser of all energized circuits contained in that structure shall be made non-automatic
How are the dielectric values of synthetic or manila rope affected when wetted?
The dielectric values of synthetic and maniia rope are similar; dry, they can be considered nonconductors, but when wet, they must be considered conductors.
Describe the generai operation of an electromechanical ground relay.
The electromechanical type of non-directional ground overcurrent relays applied in substation protective schemes use an induction disc similar to a CO or !AC type relay. The induction disc operates by torque derived from the interaction of fluxes produced by an electromagnet with those from induced currents in the plane of a rotating aluminum disc.
What steps are taken prior performing work on padmount capacitors?
The following procedures shall be completed prior to performing work on capacitors of any voltage: 1. ihe capacitors shall be de-energized using the capacitor switches provided. 2. Visually check the capacitor switches open. If any are closed, open manually with live line tools. 3. Check for elimination of current flow with clamp-on ammeter. 4. The source switch position to the capacitor switches shall be opened, locked, and tagged. Using live line tools, the primary terminals to the capacitor installation sha!! be tested de-energized and grounded. 5. After waiting a minimum of five minutes from de-energizing, the capacitor terminals shall be shorted by means of temporary jumpers and adequately bonded to the case and grounded, using live line tools.
How often is MSA Altair gas analyzer calibrated? How often are functional tests performed?
The gas monitor shall be calibrated within 30 days prior to being used. The accuracy of the instrument must be functionally checked with a known concentration of gas before each day's use. This is referred to as a "bump test."
What are the two types of ground relays used on the SCE system?
The ground relays used on the SCE system are either the electromechanlcai type, or the newer micro-processor based multi-function intelligent devices (IEDs).
When and why is rotation checked?
The need for a phase sequence meter is to identify the rotation of a three phase source and to ensure that the equipment can be reconnected to the source with the proper rotation. Before taking a piece of equipment out of service, the rotation should be checked and recorded. Then, after the work has been completed, the rotation should be rechecked before the equipment is re-energized.
How often should the neutral of a 12 kV, 4-wire circuit be grounded?
The neutral conductor of all four-wire primary circuits sha!I be grounded (t:t6 BC minimum) at intervals of approximately 1,200 feet.
When are no-test orders required?
The purpose of the "No Test Order' is to provide a formal procedure by which a qualified person, at his/her request, will receive a guarantee that a iine or equipment will not be re-energized when the nature of the work is such that re-energizing would be hazardous to personnel.
How does impedance affect the voltage of a transformer?
The voltage drop in an AC circuit is the product of the current and the ir-npedance (ZJ of the circui
What is TS-5, and when is it used?
This procedure outlines the requirements for in-place field-testing of overhead transformers. It is to be used for: • Newly installed or relocated transformers • Re-energizing existing transformers with blown fuses • CP transformers with tripped overload breakers
What is the typical function far a RO transformer, in SCE distribution?
This transformer is used to supply series streetlight circuits at a continuous 6.6 amps.
What is the purpose of a transformer tap changer?
To raise or lower secondary voitage by changing the turns ratio.
What is the distance a secondary rack is required to be above a phone cable 7
Unguarded cables, messengers or racks attached to pole: 6 feet
For what circumstance are pole grounds butt-wrapped on the pole? How is this accomplished?
Use in rocky soil where it would be impossible to drive ground rods. Use PGW wire with 10' of protective covering removed {or bare wire) on bottom of pole, and staple in place.
What is the equation for determining the load on a transformer bank with unbalanced loads?
VA= [(1.1\+ IB + IC)/3) x Ex 1.73.
What activities are prohibited when working from a boatswain chair suspended from a fiber rope?
Welding, burning, or sandblasting
When the condition of a synthetic rope that wiii be attached to an energized conductor is in doubt, what precautions should be taken?
When a rope is to be attached to an energized conductor and there is some doubt about it being wet or dry. an approved insulator (link stick, DE insufator, guy breaker, and so forth) should be used.
Explain the precautions taken when stringing wire from above or below unattached energized lines or on poles or towers on which there are attached energized lines of over 600 volts
When stringing or taking down wires from above or below unattached energized lines or on poles or towers on which there are attached energized lines of over 600 volts, precautions shall be taken to adequately insulate the employees from the wire or wire stringing equipment by the use of rubber protective equipment or other approved methods. Employees shall not contact wire stringing equipment in a manner which would permit their bodies to become a parallel path to ground. When conductors being pulled in or out are to b.e handled by employees on poles or towers, Rule 141 shall apply.
Is it permissible to go inside an area barricaded with yellow tape?
When suitable barrier tape is used to surround or isolate high voltage electrical equipment, an employee shall not be permitted to cross over or under the tape while it is barriCading an area, except in an emergency or when work in progress requires the employee to enter the hazardqus area. While in the area, the employee shall be continuously watched by another qualified employee.
Where transformers or secondaries are banked -or there is a possibility of backf eed -and the primary cutout is open, what precautions must be taken before doing any work on the primary side of the transformer?
Where secondaries of transformers are banked or there is a possibility of a backfeed, the transformer secondary leads shall be disconnected in addition to pulling prirnar1 fuses before any work is done on a transformer.
What does the term "wind loading"' mean? What are the wind standard wind load values used by SCE?
Wind loading refers to the pressure -in pounds per foot (lb/ft) -exerted on poles. The standard wind loading value is 8 lb/ft, while 6 lb/ft, 12 lb/ft, and 18 lb/ft are also used.
How is improper rotation corrected?
Without disturbing the high-leg, swap any two phases.
Are pole-mounted grounds allowed in the climbing space? If so, what provisions must be observed?
Yes, one ground wire is permitted in the climbing space, but it must be covered by an approved covering.
Under what circumstances would burn victims require medical attention?
a) Burn is larger than the size of the person's open hand. b) Burn contains blisters. c) Burn darken or breaks the skin. d) Burn involves the face, hand, foot, genitals, or skin-folds (i.e. flexural areas). e} Burn is not completely dean. f} Burn causes pain that is not relieved with over the counter pain medication (e.g. acetaminophen} or does not improve within 24 hours. g) Sum victim may have inhaled smoke. h) Burn victim has other major injuries resulting from the cause of the fire.
Determine the turns ratios for the following single-phase transformers. a. 16 kV to 120 V b. 16 kV to 240 V c. 12 kV to 120V d. 12kVto240V
a. 133:1 b. 66:1 c. 100:1 d. 50:1
What do the following colors of barrier tape indicate?
a. Orange b. Red c. Yellow d . Blue e. Purple Red: Danger or Stop Orange: Identification of hazardous parts or machines Yellow: Caution Blue: Safety Information Purple: Radiation Hazards
What are the thumb rules for determining amps per kVA for the following secondary voltages? a. 120 V single-phase b. 240 V single-phase c. 480 V single-phase d. 240 V three-phase e. 480 V three-phase f. 208 V three-phase
a. x8 b. x4 c. x2 d. x 2.4 e. x 1.8 f. x 2.8
Which type of fuses are used in a load-break fuse cabinet (LBFC)?
current-limiting-fuses (CLFs}.
If bayonet fuses must be used to de-energize a fused PM transformer, what is the maximum amperage that can be dropped? How is the load determined?
lf a transformer .is to be de-energized using the BON fuses, verify that the amperes through each BON fuse fs not in excess of 100 A, Measure th-e primary current to the transformer. Measure the primary current fee?Qing through the transformer tc other load {if applicable}. Subtract the feed through current from the current to the transformer. If this is less than 100 A, then the BON fuses may be used to de-energize the loads.
lf an empioyee is insulated from ground and other conductors while working on Edison communication open-wires, must rubber gloves be worn? Explain.
lf an empioyee is insulated from ground and other conductors while working on Edison communication open-wires, must rubber gloves be worn? Explain.
What is the industry standard for polarity markings on transformers, and how are subtractive and additive polarities indicated?
lt is an arbitrary designation, but the standard that has been set up is: Stand facing the low voltage bushing on the transformer. The high side bushing on the left hand side is assigned as the Polarity bushing. This establishes the high side poiarity only the low side polarity is established by whether it is an additive or subtractive polarity transformer. When H1 and X1 are on the same side of the transformer, it is said to be subtractive polarity. When H1 and Xl are on opposite side of the transformer, it is said to be additive polarity
Explain the differences between lrj vs. 3¢ distribution, as well as the advantages/disadvantages of each.
tn a single-phase circuit, power is delivered by only one voltage source that passes through zero every half cyde. In a three-phase circuit, even though one phase may be at zero, there are always two other phases providing power to the system or load. Because of this, the operating characteristics of three-phase apparatus, in general, are superior to those of single-phase apparatus. Some of the advantages of three-phase circuits over single-phase circuits are listed below: Generators and motors have about 50% greater output for a given amount of material. Generators, motors, transformers, and transmission equipment are more efficient. Similar distances and losses in power transmission require less conductor material. Motor starting characteristics are more satisfactory, and self-starting.
