{'fraction_non_alphanumeric': 0.01238390092879257, 'fraction_numerical': 0.0, 'mean_word_length': 5.769633507853404, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A Subtransmission Metropolitan Power Grid: Using High-Voltage dc for Enhancement and Modernization

Power demand in large or mega cities is increasing as the world urbanizes. Metropolitan transmission networks are continuously upgrading to meet the growing demand for power and to replace old-style generation with local renewable generation and power supplies from cleaner external sources. The cost of land and its scarcity make it difficult to secure new rights-of-way for traditional-style transmission lines. As power transmission levels increase, the risk of exceeding the short circuit capability of existing switchgear equipment as well as other network components becomes a major constraint to the expansion of power networks. Strategies to enhance urban transmission networks must address all of these issues and prioritize solutions that may be easily located within urban boundaries and have short lead times from decision to commercial operation. Advanced transmission technologies can effectively increase the capacity, efficiency, and utilization of existing infrastructure and improve grid resiliency under extreme contingencies or catastrophic events. These technologies have been considered and implemented by electric utilities for urban grid enhancement and modernization.