This thesis presents enhanced ultra high speed (UHS) protectivescheme that is based on the travelling wave rrw: technique. It includestwo main fault detection units; the first is analogue for primary protectionand the second is digital for secondary (backup) protection. The two unitsare combined in an integrated protective scheme with the appropriate logic.The algorithm is proposed based on simulation studies that are achieved byusing standard power system simulation software namely electromagnetictransients including DC (EMTDC). The information contained in thetravelling waves has been used to discriminate between internal andexternal faults.The analogue unit will respond directly after fault inception,however the digital unit requires analogue-to-digital (AID) conversion inaddition to algorithm processing time and may be delayed by a suitablebackup time. Therefore, the operation of the analogue unit will be faster. Ithas a fault detection operating time of 2-3 ms, The final trip decision is totransmit the trip signal to the output interface if the fault incidence ISconfirmed by the analogue unit or confirmed by the digital unit.The prototype hardware of the analogue unit was implemented andtested by a laboratory tests and its performance is found to be accepted.The algorithm of the digital unit was presented. The performance ofproposed integrated protective scheme for protecting extra high voltage(EHV) transmission lines has been tested using the simulation data andFaculty of Engineering -Zagazig University.ABSTRACTMultimedia is one of the most popular data transmitted over mobile and wirelesscommunication channels. Image encryption is often achieved by using one of threeapproaches; traditional, selective, or in-compression encryption techniques. The mostsuitable one for multimedia encryption approach is the in-compression encryptionapproach since it has the advantages of both traditional and selective techniques. As animportant way of designing a secure video encryption schemes, secret Multiple HuffmanTables (MHT) technique has been suggested as an in-compression encryption technique.However, the MHT technique suffers from high visual degradation at low bit rate and themultiple Huffman tables may be vulnerable to be known.In this thesis, a new in-compression encryption technique For efficient and securemultimedia transmission is proposed. It is a general-purpose technique meaning that it canbe used with any bit-string. It depends on a statistical model of the images to be encryptedand compressed to generate Optimized Multiple Huftinan Tables (OMHT). In this method,a set of images or videos, randomly selected from the entire set of images or videos to betransmitted, are used as a training data set to generate such optimized multiple Huffmantables. As these tables are generated from a set of images or videos of the same nature asthose to be transmitted they will be the optimal tables to encrypt and compress thetransmitted data, and hence, the name ”Optimized” is used. These tables are used toencode-encrypt the compressed image according to a secret order (secret key) whoselength is equal to the number of the generated Huffman tables. Only receivers that have thesecret key can decode/decrypt the received bit stream. The effectiveness of this scheme isverified through a series of experiments, and the robustness of developed approach isdemonstrated by comparing its performance with those of the traditional, selective.