Protection & Relay Engineer

Ryan Mahoney

Why this role is hard · Ryan Mahoney

Hiring for this role is tough because you need someone who can run station-level protection studies and knows exactly when to pause and ask for guidance. The job requires careful relay configuration and thorough acceptance testing, plus honest conversations when a setting conflicts with upstream coordination. You will immediately notice candidates who just memorize software menus but cannot explain how a fault current curve matters on a live track. Strong engineers take ownership by writing down test results and calling out risks before commissioning starts. Weak hires treat template selection like a quick checkbox and end up costing the team hours of unnecessary rework.

Core Evaluation

Critical questions for this role

The competency and attitude questions below are where the hiring decision is made. They run in the live interview rounds and are calibrated to the level selected above.

15 Competency Questions

1 of 15

  1. Discipline

    Protection And Relay Engineering

  2. Job requirement

    Cyber-Physical Integration & Advanced Monitoring

    Applies baseline cybersecurity configurations to relay networks and monitors system alarms under guidance.

  3. Expected at Junior

    Cybersecurity at this level is primarily awareness and checklist-driven application of baseline configurations, with complex network architecture and threat response handled at higher levels.

Interview round: Hiring Manager Technical Deep Dive

Tell me about a recent instance where you applied a routine configuration update or security patch to a relay system. What procedure did you follow?

Positive indicators

  • Follows documented procedures exactly
  • Verifies backups before changes
  • Acknowledges escalation paths
  • Understands basic security steps

Negative indicators

  • Applies updates without backups
  • Ignores vendor instructions
  • Attempts complex troubleshooting beyond scope
  • Dismisses prompts without review

13 Attitude Questions

1 of 13

Accountability Mindset

A cognitive and behavioral disposition characterized by an internal locus of control and systemic ownership, wherein the engineer proactively assumes responsibility for decisions, outcomes, and operational performance regardless of jurisdictional boundaries. It manifests through transparent error disclosure, blameless analytical rigor, proactive risk communication, and a continuous improvement orientation that prioritizes long-term grid reliability and safety over short-term defensiveness or credit accumulation.

Interview round: Hiring Manager Technical Deep Dive

What is your process for handling an unexpected relay test result that doesn't match your initial fault analysis?

Positive indicators

  • Treats mismatch as validation data, not failure
  • Traces discrepancy to wiring, settings, or model limits
  • Updates study documentation with test evidence

Negative indicators

  • Forces test results to match original analysis
  • Blames test equipment without investigation
  • Proceeds to energization without resolving mismatch

Supporting Evaluation

How candidates earn the selection conversation

The goal is to reduce effort for everyone by collecting more useful signal before adding more interviews. Lightweight application prompts and structured screens help the panel focus live time on the candidates most likely to succeed.

Stage 1 · Application

Filter at the door

Runs the moment a candidate hits Submit. Disqualifying answers end the application; everything else is captured for review.

Video-Response Questions

1 of 3

Application Screen: Video Response

Describe a time you had to explain complex relay coordination boundaries or fault-current thresholds to a cross-functional team that included non-specialists, such as operations managers or utility partners. How did you structure your message to ensure they understood the safety and operational implications, and what specific adjustments did you make when you sensed confusion?

Candidate experience

REC
0:42 / 2:00
1Record
2Review
3Submit

Response time

2 min

Format

Recorded video

Stage 2 · Resume Screening

Read the resume against fixed criteria

Reviewers score every application that clears the door against the same criteria. Stronger reviews advance to live interviews; weaker ones are archived without further screening.

Resume Review Criteria

8 criteria
Demonstrates hands-on experience configuring relay parameters and producing setting sheets using industry-standard protection software.
Applies power system analysis tools to develop coordination curves and calculate fault currents for discrete network segments.
Participates in or witnesses relay testing protocols to verify firmware, settings, and field performance against design models.
Shows applied experience or academic focus on protection systems within transit, rail, or battery-electric bus charging environments.

Does the cover letter or personal statement convey clear relevance and familiarity with the job?

Does the resume indicate required academic credentials, relevant certifications, or necessary training?

Is the resume complete, well-organized, and free from formatting, spelling, and grammar mistakes?

Does the resume show relevant prior work experience?

Stage 3 · During Interviews

Where the hire is decided

Interview rounds use the competency and attitude questions outlined above, then add tests, work simulations, and presentations that reveal deeper evidence about how the candidate thinks and works.

Coding Test

Live Interview · Coding Test

Without AI

Implement the provided function skeleton to parse a CSV string of fault events, group them by feeder, and calculate recommended relay pickup values. Handle malformed rows gracefully and return sorted results.

Write a Python function that ingests a CSV string containing columns: timestamp, feeder_id, fault_current_amps, fault_type. For each unique feeder_id, find the maximum fault_current_amps observed. Calculate the recommended relay pickup as max_current / safety_margin (default 1.25). Skip rows with missing or non-numeric fault_current_amps. Return a list of dictionaries sorted alphabetically by feeder_id.

With AI

Use AI to draft the core parsing logic, but you must architect how the function handles asynchronous, out-of-order data arrival common in SCADA/relay log merges. Implement your chosen timestamp reconciliation strategy and justify it in comments.

Implement calculate_relay_pickups to process fault logs that may arrive out-of-order or with slight clock drift between relay and SCADA systems. AI will likely suggest simple sorting or ignore timestamp drift. You must decide whether to implement a sliding time window, a strict sequence ID, or a tolerance-based reconciliation strategy, and justify your choice in comments. Implement your strategy to ensure deterministic results despite clock skew. Include a configuration object for tolerance thresholds and ensure the pipeline remains extensible for future telemetry sources.

Response time

20 min

Positive indicators

  • Correct CSV parsing with robust error handling for malformed rows
  • Accurate grouping and max calculation per feeder
  • Clean, readable code with appropriate type hints and comments
  • Explicitly evaluates AI-generated sorting vs. tolerance-based reconciliation and selects a robust approach
  • Implements a configurable tolerance window or sequence-based fallback
  • Documents architectural tradeoffs (e.g., memory vs. accuracy, determinism)
  • Maintains clean separation between parsing, validation, and calculation logic

Negative indicators

  • Crashes on missing data or non-numeric strings
  • Incorrect grouping logic or unsorted output
  • Hardcoded values or missing error handling
  • Accepts AI output that ignores timestamp drift or uses naive sorting without justification
  • Monolithic code with no configuration or extensibility points
  • Fails to address how out-of-order data impacts max-current calculation

Presentation Prompt

Walk us through how you would develop and validate DC feeder protection coordination curves for a new BEB depot network experiencing high inrush conditions during simultaneous multi-bus charging. Discuss how you would model the transient loads, select pickup values and time multipliers, and verify selectivity with upstream breakers.

Format

approach-walkthrough · 20 min · ~2 hr prep

Audience

Hiring manager, senior protection engineers, and commissioning lead

What to prepare

  • Review of standard DC protection coordination principles
  • Outline of your step-by-step modeling and validation approach
  • Notes on tools you would use (e.g., ETAP, SEL QuickSet) and how you would handle data gaps

Deliverables

  • A verbal walkthrough of your technical approach
  • Optional 1-2 page reference notes or whiteboard diagrams

Ground rules

  • Slides are optional; talking through your reasoning is fully acceptable
  • Use only publicly available or hypothetical data; do not share proprietary or classified utility configurations
  • Focus on your reasoning, trade-offs, and validation steps

Scoring anchors

Exceeds
Proactively identifies hidden risks (e.g., harmonic distortion, thermal limits), proposes robust validation methods, and clearly explains trade-offs with operational impact.
Meets
Outlines a logical, step-by-step coordination process, selects appropriate tools, and addresses standard BEB inrush challenges with sound engineering judgment.
Below
Provides a superficial or template-driven approach, misses key coordination boundaries, or cannot explain the rationale behind setting selections.

Response time

20 min

Positive indicators

  • Asks high-information clarifying questions about bus charging profiles and breaker capabilities
  • Surfaces assumptions about transient inrush behavior and explicitly validates them
  • Demonstrates a structured validation path from modeling to field testing
  • Articulates clear trade-offs between sensitivity and selectivity

Negative indicators

  • Jumps directly to relay settings without framing the coordination problem
  • Ignores upstream/downstream protection interactions
  • Relies on generic templates without addressing BEB-specific load dynamics
  • Fails to articulate how settings would be verified during commissioning

Work Simulation Scenario

Scenario. You are handed a preliminary one-line diagram and partial load flow data for a new Battery Electric Bus (BEB) depot. You need to develop DC feeder protection coordination curves ensuring selective tripping under high inrush conditions. The dataset has gaps, legacy relay manuals conflict with modern firmware capabilities, and the commissioning window is fixed.

Problem to solve. Drive a structured discussion to construct your approach for relay configuration and settings coordination, identifying what information you need, how you will validate assumptions, and how you will sequence your calculations before locking in settings.

Format

discovery-interview · 40 min · ~1 hr prep

Success criteria

  • Asks high-information clarifying questions to resolve data gaps before modeling
  • Explicitly surfaces assumptions and proposes verification methods
  • Sequences coordination steps logically from source to load
  • Identifies escalation triggers for complex coordination conflicts

What to review beforehand

  • Review basic DC feeder protection principles and time-current curve (TCC) overlay concepts
  • Familiarize yourself with common BEB depot charging load profiles and inrush characteristics

Ground rules

  • You will ask questions to gather information; the partner will answer honestly but will not volunteer missing data
  • Focus on your reasoning process and decision framework, not producing final calculations
  • You have 40 minutes to drive the discussion and outline your approach

Roles in scenario

Senior Protection Engineer (Peer) (informed_partner, played by peer)

Motivation. Wants to ensure the candidate can independently navigate ambiguous design inputs and produce defensible relay settings without constant oversight.

Constraints

  • Only has access to partial ETAP model files and outdated relay manuals
  • Commissioning schedule is locked by transit operations and cannot slip
  • Cannot override vendor firmware limitations without formal engineering review

Tensions to introduce

  • Load profile data shows inconsistent peak demand values across phases
  • Legacy relay pickup thresholds conflict with modern instantaneous trip curves
  • Field technicians report unexpected thermal stress on DC bus breakers during prior tests

In-character guidance

  • Answer questions directly and factually when asked
  • Provide technical context only when the candidate probes for it
  • Acknowledge realistic constraints around schedule pressure and equipment limitations

Do not

  • Do not volunteer missing parameters or data gaps before the candidate asks
  • Do not steer the candidate toward a specific relay vendor or calculation method
  • Do not solve the coordination problem or provide the final settings

Scoring anchors

Exceeds
Systematically extracts missing data, surfaces hidden assumptions, and designs a robust validation pathway that anticipates field discrepancies and firmware constraints.
Meets
Asks sufficient clarifying questions, outlines a logical coordination sequence, and identifies key verification steps without guessing or freezing.
Below
Proceeds with incomplete information, relies on copied templates, or fails to recognize critical conflicts between legacy data and modern relay capabilities.

Response time

40 min

Positive indicators

  • Asks targeted, high-information questions about load profiles, relay firmware limits, and historical fault data
  • Explicitly states assumptions and proposes field verification or secondary injection testing to validate them
  • Structures the coordination approach sequentially (source, feeder, load) and identifies selectivity margins early
  • Recognizes when legacy constraints require escalation rather than forcing incompatible settings

Negative indicators

  • Guesses missing parameters or proceeds with calculations without clarifying critical gaps
  • Freezes under ambiguity or relies on generic templates without adapting to depot-specific inrush conditions
  • Overlooks the conflict between legacy manuals and modern firmware, proposing unworkable settings
  • Fails to identify escalation triggers or verification steps before finalizing coordination curves

Progression Framework

This table shows how competencies evolve across experience levels. Each cell shows competency at that level.

Protection And Relay Engineering

6 competencies

CompetencyJuniorMidSeniorPrincipal
Cyber-Physical Integration & Advanced Monitoring

Applies baseline cybersecurity configurations to relay networks and monitors system alarms under guidance.

Implements secure communication protocols, deploys condition monitoring sensors, and investigates cyber-physical anomalies.

Designs secure OT network architectures, establishes incident response protocols for protection systems, and leads integration projects.

Defines enterprise cyber-physical security standards, pioneers AI-driven anomaly detection for protection assets, and shapes industry OT security guidelines.

Documentation, Compliance & Lifecycle Management

Updates as-built drawings, maintains relay databases, and tracks equipment warranties per established procedures.

Manages compliance audits, develops lifecycle replacement plans, and standardizes documentation templates.

Oversees enterprise asset management strategies, coordinates with regulatory bodies, and leads obsolescence mitigation programs.

Defines long-term asset lifecycle policies, integrates predictive maintenance data, and influences industry compliance frameworks for protection assets.

Grid Interconnection & Utility Interface

Prepares interconnection application documents and assists in utility coordination meetings.

Negotiates protection boundary settings with utilities, analyzes interconnection impacts, and ensures compliance with utility standards.

Manages complex interconnection projects, leads utility stakeholder engagements, and resolves jurisdictional protection conflicts.

Shapes regional interconnection policies, develops strategic utility partnerships, and architects resilient grid-tie protection frameworks for transit networks.

Protection System Design & Analysis

Performs standard fault current calculations and assists in drafting protection one-line diagrams under senior guidance.

Independently conducts complex coordination studies, selects protection devices, and optimizes system designs for reliability.

Architects multi-zone protection strategies, resolves complex coordination conflicts, and mentors engineers on design methodologies.

Defines enterprise-wide protection design standards, evaluates novel AC/DC topologies, and drives innovation in adaptive protection architectures for transit networks.

Relay Configuration & Settings Coordination

Inputs standard relay settings per manufacturer templates and verifies basic coordination under supervision.

Develops comprehensive setting files, performs time-current curve (TCC) coordination, and troubleshoots misoperations.

Establishes site-wide setting philosophies, leads complex re-coordination projects, and validates adaptive logic implementations.

Creates advanced setting algorithms for dynamic grid conditions, standardizes enterprise relay programming protocols, and advises vendors on firmware evolution.

Testing, Commissioning & Validation

Conducts routine secondary injection tests and documents results following established test procedures.

Leads complex commissioning sequences, validates end-to-end system responses, and resolves field discrepancies.

Develops comprehensive test plans for new installations, oversees contractor testing activities, and ensures regulatory compliance.

Designs next-generation automated testing frameworks, validates novel protection algorithms in lab environments, and sets enterprise QA/QC standards.