This free split-screen tool lets you explore a complete 138 kV / 13.8 kV transmission substation from two synchronized vantage points: a full 3D outdoor switchyard on the left and an IEEE single-line diagram on the right. Click any piece of equipment in the 3D scene — transformer, SF6 breaker, disconnect switch, wave trap, transmission tower — and the corresponding symbol on the one-line highlights simultaneously, while a panel shows the full engineering profile for that component. Works in the other direction too: click any SLD symbol and the 3D model highlights the physical equipment. It covers all 54 components across 8 major substation systems, from primary switchgear to relay protection, SCADA, batteries, grounding and monitoring.
The 3D scene and SLD are kept synchronized:
• 3D switchyard — two 138 kV incoming transmission circuits (lattice towers + catenary conductors), three dead-end gantries, three-phase rigid aluminum bus at 8.2 m, two 60 MVA step-down transformers with HV bushings and cooling fins, four SF6 circuit breakers, six disconnect switches, three surge arresters, current and voltage transformers, a shunt capacitor bank, shunt reactor, wave traps, and an MV switchgear lineup. • Single-line diagram — proper IEEE symbols for every electrical element: wave traps, 89 isolators, 52 breakers, the 138 kV HV bus, surge arresters, CTs, transformer differential (87T) zones, the 13.8 kV MV bus, capacitor bank, shunt reactor, three distribution feeders, and cable terminations. • 54-component catalog — every component carries its full engineering profile: code reference (IEEE / IEC standard), voltage class, function, maintenance schedule, failure modes, safety rules and operator notes. • 8 system filter chips — Primary Equipment, Protection, Control, Auxiliary Power, Grounding, Communications, Feeders, and Monitoring — isolate any system in the 3D view. • X-Ray mode — makes the control building walls transparent so you can see relay panels, SCADA cabinet, RTU, battery bank and communications rack inside. • Energized mode — transmission conductors, busbars and breaker chambers glow and pulse amber to show the live path through the substation.
Power arrives at the station on two 138 kV overhead transmission lines. Each line passes through a wave trap (line trap) — a parallel-tuned L-C circuit that blocks high-frequency power-line-carrier signals from shorting to the bus — then through a line-disconnect switch (89) providing a visible isolation point, and through a 72.5 kV class SF6 circuit breaker (52) before reaching the 138 kV main bus.
The main bus is a set of rigid aluminum tubes supported on post insulators mounted on lattice gantry structures. Surge arresters (metal-oxide varistors) connect the bus to ground to limit lightning and switching transients below equipment BIL.
Two step-down power transformers tap the HV bus through additional bus-disconnect switches, transformer breakers, and current transformers. Each transformer steps 138 kV down to 13.8 kV at 60 MVA using ONAN (oil-natural air-natural) or ONAF cooling. Transformer differential protection (87T) compares the currents on both sides and trips in under 2 cycles on any internal fault.
The 13.8 kV secondary bus feeds distribution feeders through individual feeder breakers with overcurrent and reclosing protection. A shunt capacitor bank and shunt reactor on the MV bus manage reactive power and voltage.
• Primary Equipment (cyan) — transformers, SF6 breakers, disconnects, surge arresters, CTs, VTs, busbar, capacitor bank, shunt reactor, switchgear, post insulators. • Protection (red) — line/feeder relay panels (21/67/50/51/79), transformer protection panel (87T/51/63), bus differential protection panel (87B/50BF). • Control Systems (purple) — SCADA cabinet, RTU, alarm annunciator, mimic/control board, PLC, control building, cable trenches. • Auxiliary Power (green) — 125 VDC station battery bank, battery charger, UPS, station service transformer (SSVT), AC distribution panelboard, emergency diesel generator, HVAC. • Grounding (yellow) — buried copper grounding grid (IEEE 80), ground risers, lightning/shield masts (IEEE 998), perimeter security fence (IEEE 1119), oil containment pit, fire suppression, security lighting, access road, warning signs. • Communications (teal) — fiber-optic patch panel (IEC 61850/teleprotection), telecom/carrier rack, hardened Ethernet switch, rooftop microwave and VHF/UHF antenna. • Feeders / Transmission (orange) — incoming 138 kV transmission lines, outgoing distribution feeders, underground cable terminations, dead-end gantry structures, wave traps. • Monitoring (pink) — digital fault recorder (DFR), phasor measurement unit (PMU), CCTV cameras, transformer oil monitoring, perimeter intrusion detection, badge access control, revenue metering.
A wave trap is a parallel L-C circuit connected in series with the transmission line conductor. It is tuned to the power-line-carrier (PLC) frequency band (typically 30–500 kHz) so that it presents a high impedance to carrier signals while being transparent to 60 Hz load current. Without wave traps the carrier signals — which carry teleprotection (transfer trip, line differential), voice, and SCADA — would simply short-circuit into the station bus rather than traveling to the far end of the line.
A current transformer secondary circuit must always have a low-impedance load (a relay burden or a shorting block). Under normal conditions the secondary sees a small voltage across its burden. If the secondary circuit is opened while the primary carries current, all of the primary MMF drives the core into saturation, which generates a very high, spiky open-circuit voltage — high enough to arc over and kill. The correct procedure before disconnecting any CT secondary circuit is to apply the shorting block across the terminals first.
X-Ray mode makes the control building walls transparent at 10% opacity so you can see inside: the row of protective relay panels, the SCADA gateway cabinet, the RTU, the alarm annunciator, the mimic/control board, the battery charger, UPS, fiber-optic panel, telecom rack, Ethernet switch, digital fault recorder, phasor measurement unit, and the 125 VDC station battery bank. Toggle it off to see the building as solid.
The filter chips let you isolate any of the 8 major substation systems in the 3D view. Selecting "Protection" hides everything except the relay panels; "Grounding" shows only the copper grounding grid, risers, lightning masts and fence; "Auxiliary Power" isolates the battery bank, charger, UPS, SSVT and generator. Clicking any chip highlights only that system's components in the 3D scene.
IEEE 80 (Guide for Safety in AC Substation Grounding) defines the design of the buried copper conductor mesh under the entire substation yard. During a ground fault, very large currents (tens of kiloamperes) flow through this grid to earth. The grid must be sized and laid out so that step voltage (the voltage between two feet 1 meter apart on the surface) and touch voltage (the voltage between a hand touching grounded equipment and feet on the ground) remain below the fibrillation thresholds for a person. Copper ground rods at grid intersections improve current distribution and lower overall grid resistance.