電力保安安全大会2026（一般編）

Summary

The video is an annual electrical-safety awareness session for Metropolitan Expressway staff and contractors. It explains how the expressway’s electrical supply is organized, reviews outage and electric-shock incidents, and offers practical steps to prevent electrical accidents and fires.

1. Electrical safety responsibilities and the power system

A chief electrical engineer oversees the maintenance, management, and operation of electrical equipment. Stations also have staff responsible for daily electrical-safety measures.

The conference is part of the company’s safety-management activities. Even a small lapse can lead to a serious accident. Before construction near electrical equipment, teams should identify nearby hazards, prepare a safe work plan, and confirm the arrangements with relevant workers.

The presenter describes the supply system as follows:

• Electricity arrives from the utility at high voltage—typically 6,600 V—and is transformed at substations to 100 V or 400 V for equipment such as road lighting.
• High-voltage supplies may use two lines, A and B, so that one line can continue supplying power if the other fails.
• Emergency generators can provide power during a utility outage, but they take time to start and require fuel management.
• UPS units provide immediate backup during the interruption while generators start or power sources are switched. They are used for equipment that cannot tolerate even a brief outage, such as ETC systems.
• Backup arrangements differ by location. Some substations can receive power from another substation under a prearranged power-sharing agreement; not all equipment is connected to emergency generators.

2. Outages, incidents, and coordination

The first presenter reviews several outage examples, including utility-side cable failures, damage to cables during construction, and a cable fire at a substation. These examples show that:

• Redundancy and backup systems reduce the impact of failures but do not eliminate all interruptions.
• Tunnel lighting may fall to a reduced level immediately after an outage, with generators restoring additional capacity later.
• If normal supplies and backup generation are unavailable, temporary generators may be needed for affected facilities, including toll booths and ETC equipment.
• Restoring service requires coordination among electrical staff, traffic-control teams, sales offices, maintenance contractors, and other departments. Measures may include closing toll booths, monitoring roads, notifying customers, and arranging temporary power.

The presenter also emphasizes preventing construction-related cable damage. Manuals and coordination procedures have been established for work near power and communications cables.

3. Finding and avoiding cables

Electrical and communication cables are distributed throughout expressway structures, including buried conduits, medians, earthworks, cable racks beneath structures, and tunnel walls or trenches. These may contain low-voltage, high-voltage, lighting, and communications lines.

Before excavation or other work:

• Check drawings, maintenance records, and cable-location information.
• Use manholes and other markers to help identify routes.
• Protect pipes and cable racks from damage.
• Treat nearby cables as hazardous even when they are not visible. Damage to communications lines can also disrupt systems.

4. Lessons from a serious electric-shock incident

The first presenter describes a crane accident during the removal of seasonal lighting. A crane’s wire rope approached overhead utility power lines, causing arcing and electric shocks. A later arc caused the rope to break, dropping a suspended lighting pole and damaging passing vehicles. The incident could have been fatal.

The stated contributing factors were that overhead lines had not been identified in advance and were difficult to see at night. The main lessons are:

• Identify all overhead lines before planning work.
• Follow the utility’s required separation distances and include them in work plans.
• Use company records and other available line-location resources.
• Remember that overhead lines may cause shock or arcing even without direct contact.

5. Electric-shock risks and prevention

The Kanto Electric Safety Association presenter explains that electric shock occurs when current passes through the body. Risk depends on factors such as the amount of current, how long it flows, and its path through the body; a route through the chest and heart is especially dangerous.

Key precautions include:

• Never touch fallen or damaged power lines. Keep away and contact the power company.
• Ensure appropriate equipment is properly grounded so a fault current can trigger protective devices.
• Have electrical work performed by qualified people; do not attempt unlicensed electrical construction.
• Check equipment and work areas before energizing or operating equipment.

The presenter cites workplace injury figures for 2025 and notes that electric-shock incidents are less common than many other workplace accidents but have a comparatively high fatality rate.

6. Common electrical-fire causes and prevention

The second presenter discusses several fire hazards:

• Damaged cords: Internal wires can break if cords are trapped under heavy objects, caught in doors or drawers, tightly fastened, sharply bent, or snagged. Inspect cords and avoid those conditions.
• Short circuits: Contact between conductors can produce intense heat and fire. Avoid improvised repairs or inserting objects into outlets, and use plugs and sockets as designed.
• Tracking: Dust and moisture around plugs can create a conductive path and eventually cause a fire. Unplug equipment when appropriate and clean dusty outlets and plugs with a dry cloth. Pay attention to areas under desks and behind appliances.
• Cord reels: A coiled cable reel can safely carry less current than a fully extended one. Fully extend it before use and check the product’s limits.
• Lithium-ion batteries: Avoid strong impacts and high-temperature conditions; charge and store batteries safely, check for recalls, and follow applicable transport and disposal rules. The presenter recommends products bearing the PSE mark and insulating battery terminals before disposal. Damaged or discarded batteries should be disposed of according to local rules, not left exposed outdoors.

The presentation also demonstrates that wiring mistakes can leave a plug or connector energized unexpectedly. Confirm that power is off and verify the wiring arrangement before replacing lighting or electrical components.

7. Five final requests from the safety presenter

The second presenter closes with five practical requests:

1. Do not carry out amateur electrical construction; use qualified personnel.
2. Clean and inspect electrical equipment regularly.
3. Check that equipment is safe before switching it on.
4. During a power outage, switch off equipment that was operating to avoid many machines restarting together when power returns.
5. Report anything unusual to the person in charge and handle it safely.

Speakers and sources featured

• Metropolitan Expressway Co., Ltd. electrician: First presenter; explains the company’s electrical system, outage response, cable hazards, and incident lessons. The speaker is not named in the subtitles.
• Ko, Kanto Electric Safety Association: Second presenter; discusses electric shock, electrical fires, and prevention.
• Closing host or narrator: Concludes the conference and asks viewers to complete a survey. The subtitles also mention a message from “Kate,” but the name and identity are unclear.
• Sources and materials referenced: Tokyo Electric Power Company (utility and overhead-line safety requirements); Tokyo Fire Department data on fires; Metropolitan Expressway manuals and maintenance records; the iDreams disaster-prevention website; and incident photographs, diagrams, and demonstration videos.