Power transmission and distribution were traditionally done through OHL (overhead lines), but OHL are susceptible to damage due to environmental factors such as heavy wind and lightning. Extended power outages can result in significant financial losses for power utilities, substantial production disruptions for industries, and considerable inconvenience for customers. To overcome the limitations of OH lines, underground (UG) cables are employed for power distribution.
The transition from OH power lines to underground cables involves burying electrical lines for improved aesthetics, reduced environmental impact, and enhanced reliability. It often requires significant infrastructure changes and can be more expensive but minimizes visual clutter and reduces susceptibility to weather-related disruptions. The major drawback of underground cables is identifying and repairing faults. This can result in longer outages and increased inconvenience for consumers.
Deployment of the underground power link is growing because of security considerations and upgraded dependability in the circulation frameworks. Underground cables have been of vital importance because of security threats and the need for high-voltage power in populated areas. They offer the advantage of security and are less susceptible to severe weather conditions such as high winds, lightning strikes, or heavy snowfall compared to OHL. The challenge is promptly identifying the location and nature of faults in underground cable lines. Cable failures and the precise detection of cable faults are key issues in underground cable systems.
Conventional systems
Conventional underground fault detection systems employ techniques such as monitoring insulation resistance, measuring cable parameters, or using specialized equipment to locate faults when they occur. The following are some of the conventional methods that are majorly employed for fault detection.
Technicians may visually inspect the area above ground for signs of damage to the cable, such as exposed wires, melted insulation, or scorched ground. While this method can sometimes indicate the general area of the fault, it is not precise enough for accurate fault localization.
Technicians use cable testing equipment, such as insulation resistance testers or TDRs, to assess the condition of the underground cable. These tests measure parameter like insulation resistance, capacitance, or impedance to identify abnormalities that could indicate a short circuit fault.
Thumping involves applying a high voltage pulse to the cable and listening for the distinctive sound by the discharge at the fault location. This method can help technicians narrow down the fault location by listening for the distinctive sound produced by the discharge.
Cable fault locators are specialized instruments that can help pinpoint the location of a short circuit fault along the length of the cable. These devices typically use techniques such as time domain refectory (TDR) or pulse reflection to analyze the electrical characteristics of the cable and determine the distance of the fault.
In some cases, if the fault cannot be precisely located using the methods, technicians may need to excavate the area around the suspected fault location to visually inspect the cable and perform further testing.
Cons of conventional methods:
Traditional methods lack the sensitivity to detect small or intermittent faults, leading to delayed detection and potential service interruptions.
Some conventional techniques only provide localized monitoring, making it challenging to detect faults in larger underground cable networks.
Fault identification and localization using traditional methods can be time consuming, leading to longer outage durations and increased downtime for repairs.
They have limitations in precisely locating the fault location within the underground cable network.
The proposed system helps to determine the distance of the underground cable fault from the base station in kilometers using an Arduino board. This system comprises an Arduino microcontroller, buzzer, and LCD. This reduces time and operates effectively. When a fault occurs, it is difficult to dig out the faulty underground cable without knowing its exact location of the fault. Programs uploaded to the Arduino UNO kit help detect faults in the underground cables. When a fault occurs in the underground cables, we can locate them through the Arduino controller kit. LCD display is used to display the fault distance in km.
In this proposed system, we created faults manually to test its efficacy. Every cable has a unique resistance value, which depends on the material used. The value of the resistance depends on the length of the cable. Resistance is the main function in determining the fault location. If any deviation occurs in the resistance, the value of the voltage changes at that point. Using this system, we were able to accurately locate the fault.
This project uses Ohms Law concept. When a low-voltage DC is applied to the feeder end through a series resistor, the current would differ based on the location of the fault in the cable. If there is a short circuit from line to ground, the voltage across the series resistor alters accordingly. The relay senses it, Arduino recognizes the change in voltage, and then the fault distance is displayed on LCD (16*2) display.
Design:
The following faults are created manually by closing the switches:
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These fault locations are detected by the proposed system and distance and fault phase will be showed in LCD display. The expected results are obtained in the simulation software. Thus, by using the proposed system, the drawbacks of the conventional systems can be overcome.
After review of the De Novo request, the FDA will make a final decision to either grant or decline. FDA will also consider the De Novo request to be withdrawn in certain situations.
Grant De Novo Request (21 CFR 860.260)
If the data and information provided to the FDA demonstrate that general controls or general and special controls are adequate to provide reasonable assurance of safety and effectiveness, and the probable benefits of the device outweigh the probable risks, then the FDA may grant the De Novo request and establish a new classification regulation for the new device type.
Decline De Novo Request (21 CFR 860.260)
De Novo request is declined by the FDA if –
If the De Novo request is declined, the device remains in Class III and the requester may not legally market the device. The FDA will issue a written order to the requester identifying the reasons, which can include lack of performance data that warrant declining the De Novo request. The requester should generally either submit an application for premarket approval under Section 515 of the FD&C Act or collect additional information to address the issues and submit a new De Novo request that includes the additional information.
Withdrawal of a De Novo Request (21 CFR 860.250)
The FDA will consider a De Novo classification request to be withdrawn if—
If the FDA considers a De Novo request to be withdrawn, the FDA notifies the requester with reference to the De Novo request number and the date the FDA considered the De Novo request withdrawn.
Upon receipt of a De Novo request, the FDA will conduct an acceptance review. The acceptance review is an administrative review to assess the completeness of the application and whether it meets the minimum threshold of acceptability. If any of the acceptance elements are not included, a justification has to be provided for the omission.
To aid in the acceptance review, it is recommended to submit an Acceptance Checklist as per the guidance document with the De Novo request that identifies the location of supporting information for each checklist element.
The De Novo request will not be accepted and will receive a Refuse to Accept (RTA) designation if one or more of the elements noted as RTA items in the Acceptance Checklist are not present and no explanation is provided for the omission(s). However, during the RTA review, the FDA staff has the discretion to determine whether the missing checklist elements are needed to ensure the De Novo request is administratively complete to allow the De Novo request to be accepted.
Within 15 calendar days of the Document Control Center receiving the De Novo request, the FDA will notify the requester electronically of the acceptance review result as one of the following:
Once the De Novo request is accepted for substantive review, the FDA conducts a classification review of legally marketed device types and analyzes whether an existing legally marketed device of the same type exists. This information is used to confirm that the device is eligible for De Novo classification.
During the substantive review of a De Novo request, the FDA may identify deficiencies that can be adequately addressed through interactive review and not require a formal request for additional information.
If the issues and deficiencies cannot be addressed through interactive review, an Additional Information letter will be sent to the requester. If an Additional Information letter is sent, then the De Novo request will be placed on hold. The requester has 180 calendar days from the date of the Additional Information letter to submit a complete response to each item in the Additional Information letter.
Note: The response must be sent to the DCC within 180 calendar days of the date of the Additional Information letter. No extensions beyond 180 days are granted. If the FDA does not receive a complete response to all deficiencies in the Additional Information letter within 180 days of the date of the letter, the request will be considered withdrawn and deleted from the FDA's review system. If the De Novo request is deleted, the De Novo requester will need to submit a new request to pursue the FDA's marketing authorization for that device.
The requester must submit their response to an Additional Information letter in electronic format (eCopy), to the DCC of the appropriate center. The response should—
The final step is the De Novo request decision. Under MDUFA IV, the FDA's goal is to decide about a De Novo request in 150 review days. Review days are calculated as the number of calendar days between the date the De Novo request was received by the FDA and the date of the FDA's decision, excluding the days a request was on hold for an Additional Information request.
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