Electrical Equipment Maintenance Flashcards

Comprehensive practice flashcards covering Reliability-Centered Maintenance, Power Quality disturbances, Disaster Recovery procedures, and Case Histories from NFPA 70B 2023 edition.

What is the Reliability value for a Temperature Transducer listed in Table I.5?

$$0.998242572$$

What is the Inherent Availability for a Temperature Transducer according to Annex I?

$$0.999999950$$

What is the Operational Availability for a Temperature Transducer?

$$0.999999026$$

According to Table I.5, what is the Reliability of a Dry Air Cooled Transformer?

$$0.999953743$$

What is the Operational Availability for a Dry Air Cooled Transformer?

$$0.999971899$$

What is the Reliability of a Dry Air Cooled Transformer $\le 500\,kVA$?

$$0.999775100^*$$

What is the Operational Availability for a Dry Air Cooled Transformer $\le 500\,kVA$?

$$0.999995570$$

For a Dry Air Cooled Transformer $> 1500\,kVA < 3000\,kVA$, what is the Reliability?

$$0.999393210^*$$

What is the Operational Availability for a Dry Air Cooled Transformer $> 1500\,kVA < 3000\,kVA$?

$$0.999745124$$

What is the Reliability of a Delta Wye, <600V Dry Isolation Transformer?

$$0.997166548$$

What is the Inherent Availability for a Delta Wye, <600V Dry Isolation Transformer?

$$0.999993113$$

What is the Operational Availability for a Delta Wye, <600V Dry Isolation Transformer?

$$0.999989567$$

According to Table I.5, what is the Reliability of a Forced Air Liquid Transformer?

$$0.994797669$$

What is the Operational Availability for a Forced Air Liquid Transformer?

$$0.998990580$$

What is the Reliability for a Forced Air Liquid Transformer $\le 10,000\,kVA$?

$$0.989259891$$

What is the Inherent Availability for a Forced Air Liquid Transformer $\le 10,000\,kVA$?

$$0.999836759$$

What is the Operational Availability for a Forced Air Liquid Transformer $\le 10,000\,kVA$?

$$0.996601877$$

What is the Reliability of a Liquid Non-Forced Air Transformer?

$$0.997113141$$

What is the Operational Availability for a Liquid Non-Forced Air Transformer?

$$0.999985412$$

What is the Reliability of a Liquid Non-Forced Air Transformer $\le 3000\,kVA$?

$$0.998891114$$

What is the Reliability of a Liquid Non-Forced Air Transformer $> 10,000\,kVA \le 50,000\,kVA$?

$$0.982624792$$

What is the Reliability of a Rotary UPS?

$$0.999078297$$

What is the Operational Availability for a Small Computer Room Floor UPS?

$$0.999967870$$

What is the Reliability of a 3-way Valve?

$$0.999995192$$

What is the Reliability of a Diverting/Sequencing 3-way Valve?

$$0.999257278^*$$

What is the Operational Availability for a Ball Valve, N.C.?

$$0.999998106$$

What is the Reliability of an N.O. Butterfly Valve?

$$0.999965510^*$$

What is the Operational Availability of a Check Valve?

$$0.999980199$$

What is the Reliability of a Control Valve, N.C.?

$$0.999922211$$

What is the Reliability of an Expansion Valve?

$$0.999742991^*$$

What is the Reliability of an N.O. Gate Valve?

$$0.999872337$$

What is the Reliability of an N.C. Globe Valve?

$$0.999975654^*$$

What is the Operational Availability for an N.O. Globe Valve?

$$0.999999612$$

What is the Reliability of an N.O. Plug Valve?

$$0.996093704$$

What is the Reliability of a Relief Valve?

$$0.998671145$$

What is the Reliability of an Electric Valve Operator?

$$0.990159307$$

What is the Reliability of a Hydraulic Valve Operator?

$$0.915817948$$

What is the Operational Availability for a Pneumatic Valve Operator?

$$0.999997541$$

What is the Reliability of a Static Voltage Regulator?

$$0.964377637$$

What is the Inherent Availability for a Water Cooling Coil in a Fan Coil Unit?

$$0.999999879$$

Define Inherent Availability as per Annex I.

Considers down time as a result of failure only; no maintenance down time is considered.

Define Operational Availability as per Annex I.

Considers down time as a result of both maintenance and failure.

What is the purpose of FMECA in an RCM program?

To determine failure modes effects and conduct criticality analysis of all systems to determine risk priority.

What factors determine Risk Priority in a FMECA?

The product of the severity level, failure occurrence level, and detection level.

What does RPN stand for in maintenance analysis?

Risk Priority Number

Provide the formula for calculating RPN at the component level.

$RPN = O \times S \times D$ (Occurrence x Severity x Detection)

According to 1.6.4, what is the primary purpose of preventive maintenance?

To prevent system operational failure rather than every individual component failure.

In an RCM process, what is the first step defined in Figure 1.6.5?

Define the system and identify levels of indenture.

What is constructed in step 1.6.5.3 of the RCM process?

Equipment tree (block diagram of operation between indenture levels).

When system controls and safeguards are unknown, what assumed value is assigned to the Detection Method Level?

$$1$$

What provides indication of failure frequency for equipment specific assessments in 1.6.6.2.1?

Equipment specific PREP database availability numbers.

Providing redundant components in a system has what effect on the occurrence level for a single point function?

It must be weighted to reflect presumably higher reliability and adjusted as an adjusted redundant component availability level.

What does the variable $A_i$ represent in Equation 1.6.6.2.3?

Initial inherent component availability

What does the variable $n$ represent in the adjusted redundant component availability formula?

Number of components available

According to Table 1.6.6.2.4, an occurrence rank of 1 corresponds to what availability description?

Almost Never

What is the Occurrence Rank for a component with $0.99$ availability?

$$8$$

What is the Occurrence Rank for an item with availability of $0$, described as 'Almost Certain'?

$$10$$

What occurrence description is assigned to Rank 4?

Slight

Severity pertains to and ranks what aspect of failure?

The consequences of system level failure mode effects.

What is the Ranking for a 'Very Low' effect in the Severity Rankings table?

$$2$$

A Severity Ranking of 9 or 10 is classified under what effect?

Hazard

What is the comment for a Severity Ranking of 10?

Extremely high disruption to mission

A 'High' severity effect is assigned which rank?

$$7$$

What is the formula for the Risk Priority Number of a complete system ($RPN_s$)?

$$RPN_s = \sum_{n=1}^{j} (RPN_c)_n$$

According to Table 1.6.6.4.3, what was the calculated RPN for Identifier A-1?

$$9$$

According to Table 1.6.6.4.3, what was the calculated RPN for Identifier B-1?

$$6$$

How are items with extremely low operation risk typically treated in terms of maintenance focus?

They receive low levels of maintenance focus and may be allowed to run to failure.

What is power quality?

An assessment of voltage, waveform, and frequency of the power system.

What are nonlinear loads?

Loads where the wave shape of the steady-state current does not follow the wave shape of the applied voltage.

Give three examples of nonlinear loads from Annex J.

Adjustable speed drives, switch-mode power supplies, and arcing devices (like fluorescent lamps).

What are harmonics defined as in relation to fundamental frequency?

Multiples of the fundamental frequency.

On a $60\,Hz$ power system, what is the frequency of the third harmonic?

$$180\,Hz$$

Provide the formula for Harmonic # (Equation J.2a).

$$\text{Harmonic \#} = \frac{\text{Harmonic frequency}}{\text{Fundamental frequency}}$$

What does THD stand for?

Total Harmonic Distortion

Provide the THD percentage formula from Equation J.2b.

$$THD = \frac{100 \times \sqrt{\sum V_n^2}}{V_1} \%$$

What is line voltage notching?

A form of harmonic distortion that can occur from phase-controlled rectifiers.

Where are odd triplen harmonics additive?

At the neutral circuit.

What are triplen harmonics?

Odd harmonics that are multiples of three (3rd, 9th, 15th, etc.).

At what frequency does resonance occur in a power system?

Where the shunt capacitive reactance is equal to the inductive source reactance.

What formula (Equation J.2.1) provides a first check for harmonic resonance frequency ($h$)?

$$h = \sqrt{\frac{kVA_{sc}}{kVAR_{cap}}}$$

In Equation J.2.1, what does $kVA_{sc}$ represent?

Short-circuit apparent power of source

Overvoltage conditions often occur when power system resonance approaches which harmonics?

Fifth or seventh harmonic

What is 'skin effect' in the context of harmonics?

An effect that contributes to increased winding $I^2R$ power losses due to non-uniform current distribution.

What causes counter torque and pulsating torque in motors during harmonic presence?

Negative-sequence currents from fifth harmonics.

To minimize problems, generators operating in parallel should have what common characteristic?

The same winding pitch.

A neutral-to-ground voltage exceeding what value measured at equipment suggests harmonic issues?

$$2\,V$$

What is TIF?

Telephone Interference Factor

What is the best solution for harmonic-distorted waveforms causing analog voice communication 'hum'?

Shielding or rerouting analog voice communication lines for wider separation.

What type of equipment produces harmonics when operating in the saturation region of the magnetic core?

Ferromagnetic equipment (transformers, motors, induction heaters, etc.).

What standard covers established capability of transformers supplying nonsinusoidal load currents?

ANSI/IEEE C57.110

What level of neutral-to-ground voltage measured at equipment can indicate triplen harmonics?

In excess of $2\,V$

Why should measurements for harmonic distortion be taken under different load conditions?

Because harmonic distortion can vary significantly with load.

What is one recommended solution for addressing harmonic problems related to neutral conductors?

Increased neutral conductor size.

What is a transient?

A sub-cycle voltage surge or anomaly that can damage electronic equipment components.

Lightning strikes typically cause transients through what two mechanisms?

Direct strike or induction by nearby strikes.

What units are used to rate devices intended to limit damage from transients?

Joules (watt-seconds)

Where are surge arresters typically installed?

Ahead of the service entrance equipment.

What is the purpose of a surge capacitor?

To slow the transient voltage rise time and reduce electrical stress.

What voltage range are surge protectors typically used for?

Up to $1000\,V\,rms$ or $1200\,V\,dc$

What does TVSS stand for?

Transient Voltage Surge Suppressor