The TECSYSTEM T154 WS ED25 is the latest evolution of the legendary T154—arguably the world's best-selling temperature monitoring unit for MV dry-type and cast resin transformers. It maintains the same trusted hardware platform as the standard T154 (4 Pt100 inputs, 4 relay outputs, universal power supply) while adding a groundbreaking RED-certified Wi-Fi module with integrated web server. This allows operators to monitor transformer temperatures, alarms, and historical data remotely through any web browser, without installing dedicated software or apps. The unit is 100% mechanically and electrically interchangeable with the standard T154, making it an ideal upgrade for existing installations.

Remote Monitoring Without Extra Software

• Built-in Wi-Fi Web Server: The integrated 2.4 GHz Wi-Fi module (802.11 b/g/n) with internal antenna enables complete cable-free data access. The embedded web server displays real-time temperatures, alarm status, event logs, and graphical trends accessible from any smartphone, tablet, or PC on the same network. No dedicated app installation, no software license fees, and no separate data logger hardware required.
• Automatic Data Recording ("Black Box"): The T154 WS ED25 automatically begins recording temperature data, events, and alarms from the moment it is powered on—even before any Wi-Fi configuration. This "black box" function ensures that critical temperature history is always available for post-incident analysis, regardless of whether remote access was configured.
• Dual Wi-Fi Modes: In STATION mode, the unit connects to an existing Wi-Fi network and synchronizes its internal clock via the NTP server. In ACCESS POINT mode, it creates its own Wi-Fi network, allowing direct connection even in areas without infrastructure. CSV data export enables easy integration with SCADA and plant monitoring systems.

Advanced Transformer Safety Features

• Fail Safe Function: In the event of a sensor fault (Fcc, Foc, Fcd), the FAIL SAFE function automatically simulates a maximum temperature reading on the faulty channel and activates the ALARM relay. This ensures that a broken sensor never results in undetected overheating—the control unit always fails to the safe state.
• Voting Function: The VOTING function prevents false trips caused by single-sensor anomalies. The control unit monitors all three phase sensors and votes between them: a TRIP condition is activated only when at least two sensors confirm the alarm threshold has been exceeded. This eliminates nuisance shutdowns due to localized hot spots while maintaining genuine over-temperature protection.
• Self-Diagnostic System: The unit continuously monitors the integrity of its memory, sensors, and relay outputs. Any malfunction triggers the FAULT relay and is recorded in the event log. Programming errors are clearly indicated on the display, preventing misconfiguration during commissioning. The user can also manually test all LEDs and relays by pressing and holding the TEST key.
• Auto-Scan and T-MAX: The front panel supports automatic scanning between all four Pt100 channels, manual selection of individual channels, and a T-MAX mode that continuously displays the hottest channel. This flexibility allows operators to quickly identify thermal imbalances between phases.

Easy Integration and Flexible Power Supply

• Universal Power Supply (24–240 V AC/DC): The same controller operates on any supply voltage from 24 to 240 V, both AC and DC. This eliminates the need to specify different voltage variants for different installations—one model covers control panels worldwide.
• 100% Compatible with Standard T154: The T154 WS ED25 shares the same panel cutout (92 × 92 mm), front dimensions (100 × 100 mm), terminal layout, and functionality as the standard T154. In retrofit applications, the existing wiring and panel remain unchanged—only the controller itself needs replacement.
• IP65 Front Protection: The polycarbonate front film and NORYL 94_V0 housing provide IP65 ingress protection on the front panel. The unit is certified for railway applications (EN50121-5), marine applications (RINA), and hazardous environments requiring cULus certification for North American installations.
• Pt100 Extension up to 500 m: The controller accepts 3-wire Pt100 sensors with cable lengths up to 500 meters (using 1 mm² wiring), enabling sensor placement at the transformer windings even in large substations where the controller must be located in a distant control room.

Applications

• MV dry-type and cast resin transformer temperature monitoring (3-phase + core/ambient)
• Electrical motor and generator winding temperature protection
• Substation transformer monitoring with remote SCADA and browser-based access
• Industrial process temperature monitoring requiring fail-safe relay outputs and data recording