Backup Safety Logic With Shared I/O for CCF Isolation
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Solution Overview
Problem
Existing CCF countermeasure facilities composed of analog devices require additional signal input and output devices, increasing their scale and complexity, and necessitate separation devices to prevent interference with the main protection system, leading to an increased number of components.
Innovation Solution
The safety protection system backup device employs separate but shared input and output devices for the CCF device and the main protection system, utilizing distinct communication protocols, processing units, and conversion circuits to prevent signal interference and reduce the overall scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the CCF countermeasure facility is composed of an analog facility including switches and relays, then the CCF device can be designed with relaxed design grade, but the number of signal input devices and signal output devices must correspond to the number of detectors and safety-system local components, increasing the scale of the CCF device
Solution Approach 1:
The patent merges the CCF device with the safety protection device by allowing the CCF device to access and utilize the same input devices (detectors) and output devices (safety-system local components) as the safety protection device. This sharing of I/O resources eliminates the need for separate dedicated I/O devices for the CCF device, thereby reducing the overall component count while maintaining the analog nature of the CCF device for relaxed design grade requirements
Solution Approach 2:
The input devices and output devices are designed with universal functionality to serve both the safety protection device and the CCF device. The same detector can provide signals to both devices, and the same safety-system local component can receive control signals from both devices, thereby reducing the total number of components needed in the system
2Reliability
If separation devices such as relays or fuses are provided between the CCF device and the protection-system facility to prevent electric fault influence, then the reliability is improved, but the scale of the CCF device increases due to increased number of functions
Solution Approach 1:
The patent introduces a signal isolation mechanism as an intermediary between the CCF device and the safety protection device. This isolation is achieved through the inherent architectural separation where the CCF device operates as an independent analog system that monitors and can actuate safety-system local components without requiring direct electrical connection or additional separation devices like relays or fuses, thus maintaining reliability while avoiding increased complexity
3Adaptability or versatility
If additional signal input devices and signal output devices are added to the CCF device to correspond to increased number of detectors and safety-system local components, then the adaptability is improved, but the scale of the CCF device increases
Solution Approach 1:
The patent combines the I/O resource pools of the safety protection device and the CCF device into a shared infrastructure. When the number of detectors or safety-system local components increases, the system accommodates this by utilizing the existing shared I/O resources rather than adding dedicated I/O devices to the CCF device, thereby maintaining adaptability while preventing an increase in the CCF device's scale
Solution Approach 2:
The input and output devices are designed with universal interfaces and protocols that allow them to handle signals from multiple sources and to multiple destinations simultaneously. This multi-functionality enables the system to accommodate an increased number of detectors and safety-system local components without requiring proportional increases in the number of dedicated I/O devices for the CCF device
Data Source
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AI summary
This safety protection system backup device detects a state of a plant, and then, if an abnormality is found, issues an instruction to a safety-system local component (4) according to an output of a first safety protection logic (222) in a safety protection device (2) and, if a common cause failure is found in the safety protection device (2), issues an instruction to the safety-system local component (4) according to an output of a second safety protection logic (312) in a CCF device (3). The first safety protection logic (222) and the second safety protection logic (312) are configured to execute digital signal processings based on logical configurations different from each other, whereby an input device (21) and an output device (23) can be shared by the safety protection device (2) and the CCF device (3), an input device and an output device exclusive to the CCF device (3) need not be provided, and increase in the number of detectors (1) and the safety-system local component (4) can also be dealt with without increasing the scale of the CCF device (3).