Recent progress in electronics technology has year after year elevated protection and control technology and system functions to supply high-quality electric power stably. This paper describes programmable controllers, basic components in supervision and control systems, and the lineup of hardware for protective relaying. It refers to development of their applications and the latest technical trends as well. It also contains a mention of technical subjects and trends in integrated digital systems including related apparatus for power supply.

The performance and function of protection and control systems for power supply facilities advanced every year and hardware supporting them did likewise. This paper describes the development of digital protection and control systems using a microprocessor and the lineup of recent typical hardware.
With system-type digital relays, a quite large protection and control systems can be structured around a 32-bit microprocessor, while with unit-type ones of a compact construction, distributed protection and control systems in electrical stations can be built.

Transmission lines in power systems are being extended and complicated, and the quick and precise location is demanded for better maintenance.
Fuji Electric has developed a fault locator for multiterminal transmission line utilizing the latest digital technology and supplied products for many users. It has the advantage of being able to precisely locate a fault point on a complicated transmission line with many branches.

With the vast extension and power flow confusion of power systems, the past taken by the automatic VQ controller installed in a base substation has become more and more important.
Fuji Electric has put on the market a digital automatic VQ controller in which a programmable controller is used to improve the function of former static VQ controllers. Digitization has made various improvements in the functions, precision, and operation speed.

With the recent rapid progress in microprocessor and LAN technology, supervisory control systems for substations are demanded to make improvements in maintainability, functions, and reliability to a higher grade than before.
This paper introduces the digital supervisory control system focusing our attention on necessary functions and performance, technologies applied to the system, and the system configuration.

The functions of supervision, control, and protection systems for power stations and equipment for stable high-quality power supply advance year by year.
Power stations are provided with characteristic protection and control equipment that are not in other electric stations. This paper describes the latest technologies such as the characteristics of some protective relays and the configuration of protective relaying systems citing examples mainly of protective relaying systems in hydraulic power stations and additionally of differential current relays and earth-fault excitation relays for generators.

This paper introduces a digital relay that incorporates integrated functions of protection, control, measurement, and monitoring and a function of transmission.
The aim in developing this digital relay was
(1)Improvement of system functions,
(2)Improvement of maintainability and operability by the unification of information,
(3)Reduction in cost by hardware downsizing and system simplification.

The electric railroad is a huge system composed of a lot of subsystems. Microelectronics has been applied remarkably to traction substation for trolley lines and other subsystems.
This paper gives an outline of distributed microelectronics control panels for traction substations, and also refers to unit type digital protective relays and distance relay units for protecting AC trolley lines that are used in these control panels.

This paper gives an outline of digital protection and control equipment for distributing substations, which was developed to meet needs for saving labor in maintenance and operation and improving efficiency and reliability. It is effective to make distributed system configurations.
Further, it introduces the trend of study on interconnecting protection system to connect residential photovoltaic power systems as a part of energy resources diversification to low-voltage distribution lines.

To develop and desing a protective relaying system for a power system, it is important to analyze and grasp phenomena in the power system. Further, it is necessary in the development process to verify that the produced protective relaying system grasps the aimed phenomena and operate properly without improper response to other phenomena than aimed.
This paper introduces and analog simulator and analysis technology with a computer to analyze various phenomena that happens in power systems and also the equipment and system for the verification of protective relaying systems.