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Choose your chapter The campaign runs in sequence — from a single feeder relay to the whole grid. Finish a chapter to unlock the next. Each chapter: pick the right relays for the scheme, commission the bay with the Megger toolkit, walk the relay, then configure it for real on the bench.
Act I
Distribution 13.8 kV feeders, motors and ring mains — where every protection engineer starts. Chapter 1
A Single Relay Feeder F1 — single device · 13.8 kV Your first day at the utility. The old electromechanical relay on feeder F1 finally gave up, and the senior engineer hands you a box with a numerical relay in it: 'Commission it, set it, and don't trip the bakery on load current.' 1 bay · insulation class MV Chapter 2
The Radial Feeder Single busbar · 33 / 13.8 kV Word got around that F1 trips exactly when it should. Now you own the whole substation: an incoming transformer and four feeders that must coordinate — the furthest relay trips first, the incomer is the last line of defense. 6 bays · insulation class MV Chapter 3
Split the Bus Single busbar, sectionalized · 33 / 13.8 kV A bus fault last winter blacked out the whole town for six hours. The fix is on your desk: sectionalize the busbar, add a second transformer, and make sure a fault on one section never takes down the other. 9 bays · insulation class MV Chapter 4
Spinning Iron Industrial plant MCC · 13.8 / 4.16 kV The steel plant called: their 2 MW mill motors keep cooking under unbalanced supply, and the capacitor bank they added 'to help' resonates at the worst moments. Thermal replicas, negative sequence, overvoltage — motor protection is a different art. 4 bays · insulation class MV Chapter 5
The Ring Main Ring main unit · 13.8 kV Out in the suburbs the feeders close into a ring — power can flow either way around it. Plain overcurrent can't tell which direction the fault is anymore. Time to teach your relays direction (67) before the ring teaches you humility. 4 bays · insulation class MV Act II
Substation 33–132 kV switching stations: transformers, busbars and operating flexibility. Chapter 6
The H-Scheme H-scheme (transformer feeder) · 132 / 33 kV Promotion: the 132 kV industrial intake. Two lines, two transformers, one tie — the famous 'H'. Any element can be lost without losing the plant… if, and only if, the protection is right. 5 bays · insulation class HV Chapter 7
Transformer Guardian Transformer bay · 132 / 33 kV A 40 MVA transformer costs two years of your salary budget and eighteen months of lead time. The differential relay (87T) is its bodyguard: it must trip in two cycles for a winding fault and hold dead steady for through-faults and inrush. 3 bays · insulation class HV Chapter 8
Double Busbar Double busbar · 132 kV The regional 132 kV station: every bay can pick either of two busbars, and operations re-arranges the station like furniture. Your protection has to be correct in every arrangement. 7 bays · insulation class HV Chapter 9
The Ring Bus Ring bus · 132 kV No main bus at all — the breakers themselves form a ring, and every circuit sits between two of them. Elegant, economical, and merciless: every fault must open exactly two breakers. 6 bays · insulation class HV Chapter 10
Breaker-and-a-Half Breaker-and-a-half · 220 kV The EHV interface: three-breaker diameters between two main buses, 1½ breakers per circuit. Any breaker can be maintained without an outage — which means your trip logic now has to find the *right* one and a half. 6 bays · insulation class HV Act III
Transmission 220–400 kV lines — long distances, autoreclosing, breaker-failure discipline. Chapter 11
The Long Line Transmission line terminal · 220 kV Two hundred kilometers of 220 kV across the plains. Most faults out here are lightning — gone in a flash if you reclose, permanent outages if you don't. Direction, speed and the 79 cycle are everything. 3 bays · insulation class HV Chapter 12
Double Circuit Double-circuit line · 220 kV Two circuits on the same towers — when lightning hits, it often grazes both. Your relays must reclose each circuit independently and never let a healthy circuit pay for its twin's fault. 4 bays · insulation class HV Chapter 13
Busbar Citadel Busbar protection · 220 kV A busbar fault releases the whole short-circuit strength of the grid into a few meters of aluminum. The 87B zone must clear it in under 100 ms — and if a breaker sticks, breaker-failure (50BF) has one chance to save the station. 5 bays · insulation class HV Act IV
Generation The power plant: stator windings, unit transformers and black-start auxiliaries. Chapter 14
The Generator Generator bay · 13.8 kV Inside the power plant now. A 50 MW machine: stator differential, negative-sequence heating from grid unbalance, over/underexcitation, off-nominal frequency. The machine forgives nothing — and neither does its insurer. 2 bays · insulation class MV Chapter 15
Unit Block Generator-transformer unit · 13.8 / 220 kV Generator and step-up transformer as one block, straight onto the 220 kV switchyard. Overlapping differential zones, a shared breaker, and a trip matrix where one wrong entry can shut down 200 MW. 3 bays · insulation class HV Chapter 16
Black Start Station auxiliaries · 6.6 kV Grid down. The plant must restart itself from the emergency diesel: station auxiliaries first, then the boiler feed pumps, then the unit. Undervoltage and underfrequency settings decide whether the island survives its first big motor start. 4 bays · insulation class MV Act V
The Grid Everything at once. One interconnected system, one guardian. Chapter 17
Guardian of the Grid The interconnected grid · 13.8 / 220 / 33 kV Everything you've built, connected: the plant, the switchyard, the lines, the substations, the feeders. One system, one storm rolling in tonight, and one engineer who signed every setting sheet. Protect the grid. 9 bays · insulation class HV 
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